 Section 17 of THE SCIENCE HISTORY OF THE UNIVERSE—VOLUME 6. THE SCIENCE HISTORY OF THE UNIVERSE—VOLUME 6. edited by Francis Rolt Wheeler, Zoology, Chapter 9, The Vertebrates, Part 4, Mammals, Part 5. The bears are the largest of the carnivora. They are omnivorous, or rather frugivorous, feeding mostly upon roots and berries. They are long-limbed, almost tailless, walk upon the sole of the foot, and the large sharp claws are used in digging out roots, bulbs, insects, and honey, of which last they are extremely fond. Their main subsistence in the summer is upon berries. In the north they hibernate through the winter season of scarcity and cold, coming out in the spring, hungry and ravenous, ready to season to vour anything they can find. In general, however, bears are easy-going, good-natured animals, rarely attacking men, and generally doing their best to escape when attacked, dangerous only when cornered or wounded, when hungry, or when their cubs are endangered. Perhaps an exception should be made of the polar bear, which is entirely carnivorous, living upon seals, fish, or occasional land animals, and, correspondingly, savage and temperament. The bears are chiefly a northern race, but are found in India and the East Indies, in Algeria, and in the Andes Mountains. The largest species are the huge Kediak bears of Alaska. The polar bear is almost as large. The weasel and civic families are mostly small, but bloodthirsty, and fierce beasts of prey with long tails, rather short legs, and usually slender vermi-form bodies. Most of them are terrestrial or partly arboreal, but the weasel family includes also fassorial, badgers, and semi-aquatic types, otters. The largest member of the mustelidae is the galatin, or wolverine, of the boreal zone in both old and new world. The Old World Viviridae are chiefly found in the Oriental region and in Africa. Two or three have reached the Madagascar, where they are the only carnivorous animals. The mustelidae, on the other hand, are more northern in their distribution, although found in all the great continents except Australia. The hyenas are large Old World carnivores related to the civets, but living in more open country and preying upon larger game. They are commonly called carrion eaters, but are in fact more like dogs, tracking and running down live prey, or feeding upon carcasses, pretty much as opportunity offers. They are, however, gross and indiscriminate feeders, contrasting in their manner of eating with the more dainty habits of the cats, and the teeth are massive, heavy, usually much worn on the edges. They now inhabit India, Southwestern Asia, and Africa, but formally ranged all over the northern parts of the Old World, never having reached the new. Teeth and bones of hyenas, and their prey, are the most abundant fossil remains in the bone caves of England and Northern Europe. The cats are the most strictly predacious group of carnivora. They are especially distinguished by the retractile claws, but the claws are slightly retractile in some of the vivarids, and the teeth are sharper. The shearing action of the carnasials more perfect, the crushing teeth more reduced than in any of the other families. The limbs, especially the forelimbs, are very flexible and powerful, and they afford perhaps the finest mechanical adaptations for combined strength and agility to be found in the whole animal kingdom. Although capable of great speed for a short spurt, they are not able to maintain it over long distances. They never run down their prey, but track or lie and wait for it and spring upon it unawares. If they fail to overtake it in the first few bounds, they abandon the chase. Cats are all dainty eaters, and among the thousands of skulls in large museum collections it is rare to find one with the teeth much worn, except among the desert species which must needs encounter considerable loose sand with the food. It is not true, however, that they will not devour an animal which they have not themselves killed. The largest cats are the lion and tiger, the one inhabiting Africa and southwestern Asia, the other India and eastern Asia. The lion is especially an inhabitant of desert or arid countries, and his color matches his surroundings. The brilliant vertical stripes of the tiger are said to be equally effective for concealment in the deep jungles and forests of southeastern Asia. Both are mainly nocturnal in their habits, as are all the cats. In the New World, the Puma and Jaguar correspond to the Old World lion and tiger, but are of smaller size, not exceeding the leopards of the Old World. The lynxes or bobtail cats are especially boreal in range, inhabiting the Arctic and cold temperature regions of the northern continents. Various other smaller cats range down to the size of the domestic species, inhabiting all the continents except Australia. During the latter part of the tertiary period, lived various carnivore, ancestral or related to the modern kinds. Perhaps the largest of them are the amphicyons, related to the dogs but equalling the largest bears in size, and apparently similar to them in habits. Unlike bears, they were provided with extremely long and heavy tails, exceeding those of the great cats, while the limbs were rather short. But the most remarkable of the extinct carnivora are the sabertoothed tigers, or macharodonts, related to the true cats, and similar to them in general proportions and habits, but with the upper canine enlarged into a great compressed fang, slightly curved and with sharp serrate edges. The jaws were peculiarly loose-hung, and could be opened wide enough to allow full play for the action of the tusks, and powerful muscles at the back of the skull enabled the animal to drive them down with tremendous force into the body of the enemy. The legs were short, the muscles exceptionally heavy and powerful. In all respects the sabertoothed tigers appeared to have been especially adapted to prey upon large, thick-skinned, slow-moving quadrupeds. The largest species equal to grisly bear in size, the smallest were about as large as a lynx. In the early part of the tertiary period there were numerous kinds of carnivores, with much smaller brains than the modern kinds and were primitive in various respects. These are grouped in a distinct sub-border, criodonta. Some of them were ancestral to the various families of modern carnivores. Others have left no descendants. In habits and general appearance these extinct races were much like modern beasts of prey, but the various peculiar features of the several modern races are found in different combinations. The order primates includes lemurs, monkeys, apes, and man. In this order are the animals of greatest interest on account of their near relationship to the human race. Cuvier, it is true, placed man in a separate order of mammals by mana, but almost all other zoologists, ancient and modern, are agreed in including him in the primates. Taken as a whole this order is preeminently the arboreal group among the mammalia. Its members are more completely and thoroughly specialized for this mode of life than any other group. The long slender limbs, flexible joints, opposable thumb, long toes capped with nails instead of claws, the long powerful and often prehensile tail are all peculiarly adapted to dwelling among the branches of the forest, as the teeth are to eating the fruits and berries which it affords. The highest primates, however, have departed from the typical habits of the order and become partially or completely terrestrial. It is probably to the stimulus of arboreal life that the primates owe the beginnings of that higher intelligence which distinguishes them, travel among the branches of trees, affords more continuous opportunities for the exercise of intelligent choice in determining every successive movement, then does the more uniform and safer progression upon the surface of the ground or in the water or the violent but unvarying exercise of flying. One finds that arboreal animals usually rank high in intelligence, as for instance the squirrels among the rodents, the raccoons among the carnivora, the tree shrews among insectivora, the opossums among marsupials. In addition, the opposable thumb gives to the primate a special facility in touching and handling objects and enables him to obtain readily a more exact and complete knowledge of them. In the skeleton structure, this order has departed less from the primitive mammal type than most others. As has been pointed out, the earliest mammals were probably arboreal, and the primates have retained and perfected their adaptation to this mode of life. The most notable lines of progress are in the shortening of the face and enlargement of the brain. The living primates are divided into two groups, the more primitive lemurs and the more progressive monkeys, apes and man. The lemurs are chiefly found in Madagascar, but a few of them inhabit Central Africa, India and the East Indies. They have a rather long face with less reduction in the number of teeth than the higher groups, and in all except the Tarsier, the lower incisors project forward instead of upward. The brain also is decidedly smaller and less complex, and they are very noticeably inferior to monkeys in intelligence and activity. They are, in fact, the little altered survivors of the ancestral primates of the early tertiary. Some of these ancestral primates gave rise to the more progressive higher types, while others retreated southward to the fringes of the Asiatic continents, or crossed into Africa and thence reached Madagascar. In the last named island, they found their most congenial home, free from the rivalry or pursuit of the higher type of mammals and developed into a remarkably large and varied fauna, the largest and most remarkable of which have very recently become extinct. The modern Malagasy lemurs are all arboreal, small or of moderate size, but in the late Pleistocene, probably just before man gained a foothold on the island, there were large lemurs of terrestrial adaptation paralleling some of the ungulate mammals in their skull, teeth, and skeletons, and others with remarkably short face and large brain paralleling the higher apes. These last, one may suppose, would in the course of time have evolved into creatures paralleling man himself had not their evolution when cut short by the eruption of the more progressive races developed upon the great northern land mass, in particular by the invasion of early races of man. It should be pointed out that a higher invading race destroys first those inferior races which come most directly into competition with it, while those among the native races, which are of different adaptation and habits, survive, as they do not interfere with the higher race. Man invaded the Malagasy region, probably during the Pleistocene, glacial epic. The monkeys have never reached the island. Hence the highly intelligent ground lemurs, native to the island, which came in competition with him, became extinct. The less intelligent and smaller tree lemurs have survived because they did not interfere with man and had not to compete with monkeys. Of the higher or anthropoid section of the primates, the South American monkeys are the most primitive. All of them are strictly arboreal. One family, seba day, with prehensile tails and opposable thumbs. The other, hapalidae, including only the little marmosets in which the opposability of the thumb has been lost. The marmosets are squirrel-like, in size and habits. The seba day are of larger size, but not as large as the old world monkeys and apes. In all the South American monkeys, the nostrils are separated by a broad cartilage and their apertures look outward. In the old world monkeys, as in man, the cartilage septum is much reduced. The apertures close together and facing downward. The old world monkeys and baboons are united into a single family, but are very various in proportions and appearance. The tail is sometimes long, sometimes short, and many of them are more or less terrestrial, especially the baboons. They inhabit all the tropical parts of the old world, but except for a species of maquis that lives on the rock of Gibraltar, none are found in Europe, nor do they live in Northern Asia, north of the Alti Mountains. The macacos are short-tailed, rather short-faced, asiatic in range with one species in North Africa and Gibraltar. The langhors, Semnopithecus, are long-tailed, arboreal monkeys of Southern and Eastern Asia. The Moagabes, Circocobus, are West African. The Gunos, Circopithecus, are also African, but more widely distributed. Both genera are long-tailed. The baboons, Sinocephalus, are distinguished by the projecting snout with heavy t-nineteenth. They are mostly of large size, live in herds, and are more omnivorous and ferocious than any other primates. They are all African or Arabian, except one species from Salibus, and inhabit rocky and mountainous districts living chiefly upon the ground. The last group of the primates to be considered are the anthropoid apes of the family Simeidae. These are of larger size, of higher intelligence than any other primates. Tailless, and closely allied to man in all respects. They are of arboreal habits, walking when on the ground in a semi-aract position, the long arms reaching the ground but not supporting the main weight of the body, and resting on the back of the fingers instead of the palms as on all lower animals. The skin is partly naked. The jaws, especially in the adult males, are much larger and more projecting than in man, and the brain capacity somewhat less than half of that of man, making allowance for the size of the body in different species. The four living types are the gibbons of Southeastern Asia, the gorilla and chimpanzee of the West African forests, and the orangutan of Borneo and Sumatra. It is from some unknown tertiary members of this family of apes that the ancestry of man must be derived. On account of this relationship, the anthropoid apes have been very carefully studied and described, and their appearance, habits and structure are familiar to everyone. Remains of monkeys allied to the modern South American genera have been found in the Myocene formations of Patagonia. In the Myocene of Europe have been found remains of various monkeys and lower apes of the Old World. Both are probably derived from the Eocene lemurs of Europe and North America. So far as the direct ancestry of the higher apes and man is concerned, the geological record is very incomplete. The most interesting of recent discoveries is the Pythaganthropos of Java, found upon a part of a skull and a femur, which probably, but not certainly, belong to the same individual, and indicated in animal walking upright like man, but in brain capacity, intermediate between man and the higher apes. This species, however, according to the latest investigations, was of Pleistocene age, contemporary with full developed men, so that it cannot be regarded as a direct ancestor in a genealogical sense. Since the modern species of anthropoid apes live in Africa and southern Asia, and the most primitive races of man are also found around the shores of the Indian Ocean, the theory has been advanced that it is to some part of this region that we should look for the discovery of fossil remains of the primate's ancestral to man. But in this brief review of the evolution and geological history of the lower races of mammals, it has been seen that while in the southern continents and around the southern fringes of the great northern landmass are found numerous primitive survivals of ancient races. Yet the main theater of the evolution of most races of mammals, their chief diffusion center, has always been the great landmass of the three northern continents, united more or less completely during a large part of the tertiary period. West Africa and southeastern Asia, with the East Indian islands adjoining it, contain many primitive survivals of races whose evolution center was in the Palearctic region. In the present writer's opinion, the geological evidence of the ancestry of man and the most direct phyllogeomy of many mammals will be discovered when the tertiary formations of central and eastern Asia are adequately and thoroughly searched for remains of fossil vertebrates. At present they are practically unknown. From the observations of pioneer explorers it is very probably inferred that fossiliferous formations of tertiary age exist in some parts of this immense region. The revealing of the evidence, which they should afford of the true evolutionary history of the higher mammals and of man, is the task for the scientific explorers of the 20th century. Section 18 of The Science History of the Universe, Volume 6. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org. Recording by Avae in November 2019. The Science History of the Universe, Volume 6. Edited by Francis Rold Wheeler Botany, Chapter 1. Early Development What is the content and scope of the science of botany? asks Professor Herbert Maul Richards in a recent lecture and his reply is very true. Popular opinion, he says, will answer somewhat easily. Botany consists in the gathering of plants and the dismembering of them in connection with the use of a complicated terminology. That is the beginning and end of botany as it is understood by the majority. There is nothing more to be said. In consequence, the employment of the botanist seems so trivial, so very remote from important human interests that no second thought is given to it. The conception formed in ignorance is continued in ignorance. Even the zoologist is at an advantage, for the public is finally forced to admit that it does not know what he is about, while it understands the botanist very well. He is quite hopeless, for while flowers may be pretty things to pick, they should not be pulled to pieces, and if he does not happen to be interested in dissecting flowers, he is not a botanist, but simply a fraud. Under botany we have to consider all the questions as to the form, functions, the classification, and the distribution of those organisms that are called plants. In the beginning all that was known about plants might be readily comprehended under the simple caption botany, but in modern times the rapid accumulation of facts has demanded a segregation of different lines of work. Thus have arisen the divisions of botanical activity, which for our purposes may be classed under three heads. First the taxonomic, or as more commonly called the systematic side, which has to do with the classification, mainly as established by gross morphology. Second the morphological field, which concerns itself with the outward and inward form and structure and the development thereof, which may or may not have direct relation with taxonomic work. Third there is the domain of physiology, which treats of function. Any folk which had so far emerged from the stage of savagery as to stop to notice the world about it would perforce pay some attention to plants. A discrimination of the medicinal uses of plants is often noticeable even in primitive peoples, and with such observation goes also the discrimination of difference in form, the prototype of morphological research. In our own civilization we can trace back the history of botany to Aristotle, who affords us some record of the plant forms known at his time, though the influence which his philosophy wielded, even down to the middle of the last century, was of vastly greater importance than any contribution which he made to botany itself. Theophrastus gave a fuller account of plants, and later came the inquiring and ever curious pliny. Dioscorides however, in the first or second century of our era, was one of the first to investigate plants with any attempt to thoroughness, even from the standpoint of the knowledge of the time. As is shown especially by Dioscorides work, the study of plants was largely from their users' drugs, and they were described simply to facilitate their recognition. Any real knowledge of them was naturally meager, and false ideas that clung for a long time, some until comparatively recently, prevented any proper conception of form and function. The contributions become of less and less value as we approach the Middle Ages, the botanical writings of which time are full of the wildest fantasy and superstition. In the 16th century in Northern Europe, particularly Germany, there was a movement toward the real study of plants from the plants themselves, as evidenced by the works of the herbalists, but no attempt at classification was made. Here there was an attempt at the enumeration and illustration of plants from living specimens, and confused and empirical as this work was, it was actuated by an honest endeavour to record, as accurately as possible, actual forms, and not fanciful abstractions which never did, and never could have existed. All the descriptions were detached from one another, and little or no attempt was made at classification, though by the repeated study of many similar forms the idea of natural relationship began to dawn in a vague way. The actual purpose of all this plant study was the recording of the officinal plants, for special knowledge of plants was still confined to their users in medicine. While this movement was advancing in Northern Europe, a mainly artificial system of classification was developing in Italy, and found its culmination in the work of Cesar Pino, who strongly influenced the progress of botany, even after his own time and into the middle of the 18th century. As the nature of plants, so begins Cesar Pino's book, possesses only that kind of soul by which they are nourished, grow, and produce their like, and they are therefore without sensation and motion in which the nature of animals consists, plants have accordingly need of a much smaller apparatus of organs than animals. This idea reappears again and again in the history of botany, and the anatomists and physiologists of the 18th century were never weary of dilating on the simplicity of the structure of plants and of the functions of their organs. But since the function of the nutritive soul consists in producing something like itself, and this like has its origin in the food for maintaining the life of the individual, or in the seed for continuing the species, perfect plants have at most two parts, which are however of the highest necessity, one part called the root by which they procure food, the other by which they bear the fruit. This conception of the upright stem as the seed bearer of the plant, which is in the main correct, also was long maintained in botany. It should be observed also that the production of the seed is spoken of as merely another kind of nutrition, a notion which afterward prevented Malpigi from correctly explaining the flower and fruit, and in a modified form led Kaspar Friedrich Wolff in 1759 to a very wrong conception of the nature of the sexual function. The next sentence in César Pino leads into the heart of the Aristotelian misinterpretation of the plant, according to which the root answers to the mouth or stomach and must therefore be regarded in idea as the upper part, although it is the lower in position, and the plant would have to be compared with an animal set on its head and the upper and lower parts determined accordingly. César Pino's discussion of the seed of the soul in plants is of special interest in connection with certain views of later botanists. Whether any one part in plants can be assigned as the seed of the soul, such as the heart in animals, is a matter for consideration, he says. For since the soul is the active principle, actus, of the organic body, it can neither be tota in toto nor tota in singulis patipus, but entirely in some one and chief part, from which life is distributed to the other dependent parts. If the function of the root is to draw food from the earth and of the stem to bear the seeds, and the two cannot exchange functions, so that the root should bear seeds and the shoot penetrate into the earth, there must either be two souls different in kind and separate in place, the one residing in the root, the other in the shoot, or there must be only one, which supplies both with their peculiar capabilities. It may be remarked here, says Julius von Sacks in his history of botany, that the point of union between the root and the stem, in which Cesar Pino placed the seed of the plant soul, afterward received the name of root-neck, call it. And though the Linnaean botanists of the nineteenth century were unaware of what Cesar Pino had proved in the sixteenth, and did not even believe in a soul of plants, they still entertained a superstitious respect for this part of the plant, which is really no part at all. And this, it would seem, explains the fact that an importance scarcely intelligible without reference to history was once attributed to it, especially by some French botanists. The theoretical introduction to his excellent and copious remarks on the parts of fruitification may supply another example of Cesar Pino's peripatetic method. As the final cause, finis of plants consists in that propagation which is affected by the seed, while propagation from a shoot is of a more imperfect nature, insofar as plants do exist in a divided state, so the beauty of plants is best shown in the production of seed, for in the number of the parts and the forms and varieties of the seed vessels, the fruitification shows a much greater amount of adornment than the unfolding of a shoot. This wonderful beauty proves the delight, delitas, of generating nature in the bringing forth of seeds. Consequently, as in animals, the seed is an excretion of the most highly refined food substance in the heart, by the vital warmth and spirit of which it is made fruitful, so also in plants it is necessary that the substance of the seeds should be secreted from the part in which the principle of the natural heat lies, and this part is the pith. For this reason, therefore, the pith of the seed, that is the substance of the cotyledons and of the endosperm, springs from the moisture and purer part of the food, while the husk which surrounds the seed for protection springs from the coarser part. It was unnecessary to separate a special fertilizing substance from the rest of the matter in plants as it is separated in animals which are thus distinguished as male and female. This last remark and some lengthy deductions which follow are intended to prove, after the example of Aristotle, the absence and indeed the impossibility of sexuality in plants, and accordingly Cesar Pino goes on to compare the parts of the flower, which he knew better than his contemporaries, with the envelopes of the ova in the fetus of animals, which he regards as organs of protection. The doctrine of metamorphosis, suggests Fonsacs, appears in a more consistent and necessary form in Cesar Pino than in the botanists of the 19th century before Darwin. It flows more immediately from his philosophical views on the nature of plants and appears therefore up to a certain point thoroughly intelligible. We see in Cesar Pino's doctrine of metamorphosis, without doubt, the theory of the flower afterward adopted by Linnaeus, though in a somewhat different form. That Linnaeus himself regarded the theory ascribed to him on the nature of the flower as the opinion of Cesar Pino also, is shown in his classes Planetarum, where in describing Cesar Pino's system he says, he regarded the flower as the interior portions of the plant, which emerged from the bursting rind, the callix as a thicker portion of the rind of the shoot, the corolla as an inner and thinner rind, the stamens as the interior fibers of the wood, and the pistil as the pith of the plant. But, to do Cesar Pino justice, it would be necessary to give a full account of his very numerous, accurate and often acute observations on the position of leaves, the formation of fruits, the distribution of seeds and their position in the fruit, of his comparative observations on the parts of the fruit in different plants, and above all of his very excellent description of plants with tendrils and climbing plants, of those that are armed with thorns and the like. Though there is naturally much that is erroneous and inexact in his accounts, yet in the chapters on these subjects may be seen the first beginning of a comparative morphology, which quite casts into the shade all that Aristotle and Theophrastus have said on the subject. But the most brilliant portions of his general botany are those in which he gives the outlines of his views on the systematic arrangement of plants. All that Cesar Pino says on systematic arrangement shows that he was perfectly clear in his own mind with regard to the distinction between a division on subjective grounds, and one that respects the inner nature of plants themselves, and that he accepted the latter as the only true one. He says, for instance, we seek out similarities and dissimilarities of form in which the essence, substancia, of plants consists, but not of things which are merely accidents of them, quite accidentipsis. Medicinal virtues and other useful qualities are, he says, just such accidents. Here the path is opened, along which all scientific arrangement must proceed, if it is to exhibit real natural affinities. But at the same time there is a warning already of the error which beset systematic botany up to Darwin's time, if in the above sentence he substituted the word idea for that of substance, and the two expressions have much the same meaning in the Aristotleian and Platonic view of nature, will be recognized the modern pre-Darvinian doctrine, that species, genera, and families represent ideam-quandam and quodam supranaturale. The next great figure in botanical science was Joachim Jung. He was born in Lübeck in the year 1587, and died after an eventful life in 1657. He was a contemporary of Kepler, Galileo, Vesal, Bacon, Cassendi, and Descartes. After having been already a professor in Giesen, he applied himself to the study of medicine in Rostock, was in Padua in 1618 and 1619, and there, as may confidently be believed, became acquainted with the botanical doctrines of Cesar Pino, which had died 15 years before. He occupied himself with the philosophy of the day, in which he appeared as an opponent of scholasticism and of Aristotle, and also with various branches of science, mathematics, physics, mineralogy, zoology, and botany. In 1662, his pupil, Martin Fogel, printed the Toxoscopie Physicae Minores, a work of enormous compass left in manuscript at the master's death, and another pupil, Johann Vagetius, the Isagoge Fitoscopia in 1678. Ray, however, states that a copy of notes on botanical subjects had already reached England in 1660. He was the first to object it to the traditional division of plants into trees and herbs as not founded on their true nature. But how firmly this old dogma was established is well shown by the fact that Ray, at the end of the century, still retained this division, though he founded his botanical theories on the Isagoge of Jung. Jung was in advance of Cesar Pino and his own contemporaries in repeatedly expressing his doubt of the existence of spontaneous generation. The Isagoge Fitoscopica, a system of theoretical botany, says Fonsacs, very concisely written and in the form of propositions arranged in strict logical sequence, was a more important work and had more lasting effects upon the history of botany. The first chapter of the Isagoge discusses the distinction between plants and animals. A plant is, according to Jung, a living but not a sentient body, or it is a body attached to a fixed spot or a fixed substratum from which it can obtain immediate nourishment, grow and propagate itself. A plant feeds when it transforms the nourishment which it takes up into the substance of its parts, in order to replace what has been dissipated by its natural heat and interior fire. A plant grows when it adds more substance than has been dissipated and thus becomes larger and forms new parts. The growth of plants is distinguished from that of animals by the circumstance that their parts are not all growing at the same time, for leaves and shoots cease to grow as soon as they arrive at maturity, but then new leaves, shoots and flowers are produced. A plant is said to propagate itself when it produces another specifically like itself. This is the idea in its broader acceptance. We see that here, as in Cesar Pino, the idea of the species is connected with that of propagation. The second chapter, headed Plante Partizio, treats of the most important morphological relations in the external differentiation of plants. Here Jung adheres essentially to Cesar Pino's view that the whole body in all plants, except in the lowest forms, is composed of two chief parts, the root as the organ which takes up the food and the stem above the ground which bears the fruitification. Jung's theory of the flower suffers, as in Cesar Pino, from his entire ignorance of the difference of sexes in plants, which is sufficient to render any satisfactory definition of the idea of a flower impossible. While Cesar Pino, Kaspar Bauhin and Jung stand as solitary forms each in his own generation, the last 30 years of the 17th century are marked by the stirring activity of a number of contemporary botanists. While during this period, physics was making rapid advances in the hands of Newton, philosophy in those of Locke and Leibniz, and the anatomy and physiology of plants by the labourers of Malpegi and Gru, systematic botany was also being developed, though by no means to the same extent or with equally profound results, by Morrison, Ray, Bachman, Rivenos and Dornfort. The works of these men and of their less gifted adherents, following rapidly upon or partly synchronous with each other, led to an exchange of opinions and sometimes to polemical discussion, such as had not before arisen on botanical subjects. This abundance of literature, with the increased animation of its style, excited a more permanent interest, which spread beyond the narrow circle of the professional adepts. Carl Linnaeus, called Carl von Linnae after 1757, was born in 1707 at Rasshult in Sweden, where his father was preacher. Linnaeus is commonly regarded as the reformer of the natural sciences, which are distinguished by the term descriptive, and it is usual to say that a new epoch in the history of our science begins with him as a new astronomy began with Copernicus and new physics with Galileo. This conception of Linnaeus' historical position, von Sachs points out, as far at least as his chief subject, botany, is concerned, can only be entertained by one who is not acquainted with the works of Cesar Pino, Jung, Ray and Bachman, or who disregards the numerous quotations from them in Linnaeus' theoretical writings. On the contrary, Linnaeus is preeminently the last link in the chain of development represented by the above-named writers. The field of view and the ideas of Linnaeus are substantially the same as theirs. He shares with them in the fundamental errors of the time, and indeed, essentially contributed to transmit them to the 19th century. But to maintain that Linnaeus marks not the beginning of a new epoch, but the conclusion of an old one, does not at all imply that his labours had no influence upon the time that followed him. If the works of the earlier botanists are compared with Linnaeus' Fundamenta Botanica 1736, his Classes Planetarum 1738, and his Philosophia Botanica 1751, it becomes evident that the ideas on which his theories are based are to be found scattered up and down in the works of his predecessors. Further, whoever has traced the history of the sexual theory from the time of Camerarius 1694, must allow that Linnaeus added nothing new to it, though he contributed essentially to its recognition. But that which gave Linnaeus so overwhelming an importance for his own time was the skillful way in which he gathered up all that had been done before him. His fusing together of the scattered acquisitions of the past is the great and characteristic merit of Linnaeus. César Pinot was the first to introduce Aristotelian modes of thought into botany. His system was intended to be a natural one, but it was in reality extremely unnatural. Linnaeus, in whose works the profound impression which he had received from César Pinot is everywhere to be traced, retained all that was important in his predecessors' views, but perceived at the same time what no one before him had perceived, that the method pursued by César Pinot could never do justice to those natural affinities which it was his object to discover, and that in this way only an artificial, though very serviceable, arrangement could be attained, while the exhibition of natural affinities must be sought by other means. Section 19 of The Science History of the Universe Volume 6 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org, recording by Avaii in February 2020. The Science History of the Universe Volume 6 edited by Francis Rold Wheeler. Botany Chapter 1 Early Developments of Botany Part 2 As regards the terminology of the parts of plants, which was all that the morphology of the day attempted, Linnaeus simply adopted all that was contained in the isogogue of young, but gave it a more perspicuous form, and advanced the theory of the flower by accepting, without hesitation, the sexual importance of the stamens, which was still but little attended to. He thus arrived at a better general conception of the flower, and this bore fruit again in a terminology which is as clear as it is convenient. But there was one great misconception in the matter, which has not a little contributed to increase Linnaeus's reputation. He called his artificial system, founded on the number, union and grouping of the stamens and carpels, the sexual system of plants, because he rested its supposed superiority on the fact that it was founded upon organs, the function of which lays claim to the very highest importance. But it is obvious that the sexual system of Linnaeus would have the same value for the purposes of classification, if the stamens had nothing whatever to do with propagation, or if their sexual significance were quite unknown. For it is exactly those characters of the stamens which Linnaeus employs for purposes of classification, their number and mode of union, which are a matter of entire indifference as regards the sexual function. Linnaeus distinctly declared it was his view that the highest and only worthy task of a botanist was to know all species of the vegetable kingdom exactly by name, and his school in Germany and England adhered to it so firmly that it established itself with the general public, who to the present day consider it as a self-evident proposition that a botanist exists essentially for the purpose of at once designating any and every plant by a name. Like his predecessors, Linnaeus regarded morphology and general theoretical botany only as a means to be used for discovering the principles of terminology and definition, with a view to the improvement of the art of describing plants. The most pernicious feature in scholasticism and the Aristotelian philosophy is the confounding of mere conceptions and words with the objective reality of the things denoted by them, says Von Sacks upon this point. Men took a special pleasure in deducing the nature of things from the original meaning of the words, and even the question of the existence or non-existence of a thing was answered from the idea of it. This way of thinking is found everywhere in Linnaeus, not only where he is busy as systematist and describer, but where he wishes to give information on the nature of plants and the phenomena of their life. Linnaeus cared little for experimental proof. He expends all his art on a genuine scholastic demonstration intended to prove the existence of sexuality as arising necessarily from the nature of the plant. On the whole, the superiority of Linnaeus lay in his natural gift for discriminating and classifying the objects which engaged his attention. He might almost be said to have been a classifying, coordinating and subordinating machine. He dealt with all about which he wrote in the way in which he dealt with objects of natural history. In any attempt to estimate the advance which the science owes to the labourers of Linnaeus, says the former writer, the chief prominence must be assigned to two points. First, to his success in carrying out the binary nomenclature in connection with the careful and methodical study which he bestowed on the distinguishing of genera and species. The system of nomenclature he endeavoured to extend to the whole of the then known vegetable world, and thus descriptive botany in its narrower sense assumed through his instrumentality an entirely new form. The second merit is that while he framed his artificial sexual system, he exhibited a fragment of a natural system by its side and repeatedly declared that the chief task of botanists is to discover the natural system. Thus he cleared the ground for systematic botany. The main features of Linnaeus' theoretical botany can best be learned from the philosophia botanica, which may be regarded as a textbook of that which Linnaeus called botany, and which far surpasses all earlier compositions of the kind in perspicuity and precision and in copiousness of material. And indeed it would be difficult to find in the ninety years after 1781 a textbook of botany which treats what was known on the subject at each period with equal clearness and completeness. The vegetable world says Linnaeus comprises seven families, fungi, algae, mosses, ferns, grasses, palms, and plants. All are composed of three kinds of vessels, sap vessels which convey the fluids, tubes which store up the sap in their cavities, and trachea which take in air. These statements Linnaeus adopts from Malpegi and Gru. The parts in the individual plant which the beginner must distinguish are three, the root, the herb, and the parts of fructification, in which enumeration Linnaeus departs from his predecessors, by whom the fructification and the herb together are opposed to the root. In the central part of the plant is the pith, enclosed by the wood which is formed from the past. The past is distinct from the rind which again is covered by the epidermis. These anatomical facts are from Malpegi. The statement that the pith grows by extending itself and its envelopes is borrowed from Mariot. The root which takes up the food and produces the stem and the fructification consists of pith, wood, past, and rind and is divided into the two parts, cortex, and radicular. The cortex answers pretty nearly to the modern primary root and rhizomes, the radicular to what is now called secondary roots. The herb springs from the root and is terminated by the fructification. It consists of the stem, leaves, leaf supports, fulcrum, and the organs of hibernation, hibernaculum. Then follow the further distinctions of stem and leaves. The terminology, still partly in use and resting essentially on the definitions of yung, is here set forth in great detail. Linnaeus however does not mention the remarkable distinction between stem and leaf which yung founded on relations of symmetry. In this course of mixing up morphological and biological relations of organs he was followed by botanists till late into the 19th century. Linnaeus goes far beyond his predecessors in distinguishing and naming the organs of fructification. The fructification he says is a temporary part in plants devoted to propagation, terminating the old and beginning the new. He distinguishes the following seven parts. One, the calyx, which represents the rind, including in this term the involucre of the umbilifere, the spath, the calyptra of mosses, and even the vulva of certain fungi. Another instance of the way in which Linnaeus was guided by external appearance in his terminology of the parts of plants. Two, the corolla which represents the inner rind past of the plant. Three, the stamen which produces the pollen. Four, the pistil which is attached to the fruit and receives the pollen. Here for the first time the ovary, stile and stigma are clearly distinguished. But next comes as a special organ. Five, the pericarp, the ovary which contains the seed. Nevertheless, Linnaeus distinguishes the different forms of fruit much better than his predecessors had done. Six, the seed is a part of the plant that falls off from it, the rudiment of a new plant, and it is excited to achieve life by the pollen. The treatment of the seed and its parts is the feeblest of all Linnaeus's efforts. He follows kesalpino, but his account of the parts of the seed is much more imperfect than that of kesalpino and his successors. Seven, by the word receptaculum he understands everything by which the parts of the fructification are connected together. Both the receptaculum proprium, which unites the parts of the single flower, and the receptaculum commune, under which term he comprises the most diverse form of inflorescence, umbil, syme, spadex. He concludes with the remark that the essence of the flower consists in the anther and the stigma, that of the fruit in the seed, that of the fructification in the flower and the fruit, and that of all vegetable forms in the fructification. And he adds a long list of distinctions between the organs of fructification with their names. Among these organs appear the nectaries, which he was the first to distinguish. From Linnaeus the advance was more rapid, and while most of the study in plants centered on the work of classification, there were unmistakable signs of other interests. The ideas of the classified were still hampered by the dogma of the constancy of species, which continually clashed with the insistent and undeniable evidences of the genetic relationships of organic forms. Despite the movement in favor of the idea of the development of species from previously existing forms, despite the views advanced by Lamarck and others at about that time, despite indeed the more strictly botanical investigations in the morphological field, which were brought forward during the first half of the 19th century, despite all these things, the botanist was unable to break away from the concept of groups of plants as abstract ideas. It was not until 1859 that the publication of Darwin's Origin of Species drove biologists to a different point of view. Then the rational idea of the evolution of organic forms explained in a similar rational fashion the observed genetic relationships of groups of plants. No longer, says Richards, did the classifier hesitatingly admit the possibility of the evolution of species and deny that of genera and higher groups. No longer did he maintain his artificial groups, which had no more relation to each other than successive throes of dice, but he admitted the whole great scheme implied by the evolution of organic forms from pre-existing types. The natural system was rightly appreciated by Linnaeus, says Azar Gray in his Structural Botany, who pronounced it to be the first and last desideratum in systematic botany, and he early attempted to collocate most known genera under natural orders, but without definition or arrangement. In his later years he was unable to accomplish anything more. The difficult problem was taken up by Linnaeus' contemporary and correspondent Bernard de Jussieux. His pupil, Adenson, published in 1763 in his Familles de Plante, the first complete system of natural orders. Adenson himself thus defines his idea of species. The moderns define a species of plant as a collection of several individuals which resemble each other perfectly, yet not in everything, but in the essential parts and qualities, without, however, giving attention to the differences caused in these individuals either by sex or accidental varieties. Antoine Laurent de Jussieux, nephew of Bernard, followed Adenson. He has been called the founder of the natural system of botany, says Azar Gray, and to him more than to any other person this honour may be ascribed. In his Genera Plantanum Secundum Ordines Naturales Disposita, 1789, natural orders of plants, one hundred in number, were first established and defined by proper characters, and nearly all known genera arranged under them. The next great systematist was Auguste Puram de Candol, Reversing the order of Jussieux, who proceeded from the lower or simpler to the higher or more complex forms, de Candol began with the latter, the phenogamous or flowering plants, and with those having typically complete flowers. The Candol's interest was perhaps more from a morphological point of view, although he is to be regarded as a systematist, and from that standpoint it will be seen later that his work was of the first importance. John Lindley in successive attempts between 1830 and 1845 variously modified and in some few respects improved the Candolian arrangement. Robert Brown, next to Jussieux, did more than any other botanist for the proper establishment and correct characterization of the natural orders. Stephen Ladislaus Endliker of Vienna, a contemporary of Lindley, of less botanical genius, but of great erudition and aptness for classification, brought out his complete genera plantarum secundum ordines naturales disposita between the years 1836 and 1840. The genera plantarum of Bentham and Hooker adopts in a general way the Candolian sequence of order with various immendations, divides the class of dichotillidens into two subclasses, angiosperms and gymnosperms, with still further divisions in the angiosperms. In this country botanists have to thank the labors of John Torrey and Azar Gray for the firm foundation upon which the knowledge of American flora is built. Of the two, Azar Gray was by far the broader in his interests and is regarded by many as the father of American botany. He had considerable knowledge of other fields than that of mere systematic botany of the higher plants and was perhaps the ablest protagonist whom Darwin had in this country. He wrote numerous papers in defense of the then new theory of the origin of species. His main work, however, was the taxonomic study of the flora of North America. Discussion of the definition of species, how much a species includes and of what constitutes a variety, is at present a foremost question among taxonomists and the effort seems to look towards simplification and lessening of the numbers already formed. Linnaeus tells in his Philosophia Botanica, 1751, we enumerate as many species as different forms we originally created. He also says, there are as many species as the infinite being originally produced different forms, and these forms, following the laws of reproduction imposed upon them, have produced more but always similar to themselves. Therefore, there are as many species as there are different forms or structures met with today. The idea of a species set forth by Lamarck is thus defined. In botany, as in zoology, a species is necessarily constituted of the aggregation of similar individuals which perpetuate themselves, the same by reproduction. I understand similarity in the essential qualities of the species, because the individuals which constituted offer frequently accidental differences, which give rise to varieties and sometimes sexual differences, which belong, however, to the same species, as the male and female hemp, in which all the individuals constitute the common cultivated hemp. Thus, without the constant reproduction of similar individuals, there could not exist a true species. The Kandol and Sprengel say that, by species, we understand a number of plants which agree with one another in invariable marks. No doubt, there were in the preceding state of our globe other species of plants which have now perished, and the remains of which we still find in impressions in shale, slate clay and other flutes rocks. Whether the present species, which often resemble these, have arisen from them. Whether the present species, which often resemble these, have arisen from them. Whether the great revolutions on the surface of the earth, which we read in the Book of Nature contributed to these transitions, we know not. What we know is that from as early a time as the human race has left memorials of its existence upon the earth, the separate species of plants have maintained the same properties invariably. To be sure, we frequently speak of the transitions and crossings of species, and it cannot be denied that something of this idea does not occur, though without affecting the idea of species which we have proposed. We must therefore understand this difference. Species only appear to undergo transitions when we have considered an organ or a property as invariable, which is not so. All properties of plants which are subject to change form either a subspecies or a variety. By the former we understand such forms as continue indeed during some reproductions, but at last by a greater difference of soil, of climate and of treatment, are either lost or changed. John Lindley in his Introduction to Botany defines species as a union of individuals agreeing with each other in all essential characters of vegetation and fructification, capable of reproduction by seed without change, breeding freely together, and producing perfect seed from which a fertile progeny can be reared. To Asa Gray, species in biological natural history is a chain or series of organisms of which the links or component individuals are parent and offspring. Objectively, a species is the totality of beings which have come from one stalk, in virtue of that most general fact that likeness is transmitted from parent to progeny. The two elements of species are one, community of origin and two, similarity of the component individuals. But the degree of similarity is variable and the fact of genetic relationship can seldom be established by observation or historical evidence. It is from the likeness that the naturalist ordinarily decides that such and such individuals belong to one species. Still, the likeness is a consequence of the genetic relationship, so that the latter is the real foundation of species. Varieties are forms of species marked by characters of less fixity or importance than are the species themselves. They may be of all grades of difference from the slightest to the most notable, they abound in free nature, but assume particular importance under domestication and cultivation, under which variations are prone to originate and desirable ones are preserved, led on to further development and relatively fixed. Charles Darwin, whose work has done so much to put all natural sciences upon their present basis of experimental observation, does not commit himself to an actual statement. He says that no one definition has satisfied all naturalists, yet every naturalist knows vaguely what he means when he speaks of a species. The term variety is almost equally difficult to define, but here community of descent is almost universally implied, though it can rarely be proved. All the individual plants which resemble each other sufficiently to make us conclude that they are all, or may have been all, descended from a common parent, are included in one species by George Bentham. These individuals may often differ from each other in many striking particulars, such as the colour of the flower, size of the leaf, etc., but these particulars are such as experience teaches us are liable to vary in the seedlings raised from one individual. When a large number of the individuals of a species differ from the others in any striking particular, they constitute a variety. Britain and Brown consider that a species is composed of all the individuals of a kind capable of continuous successive propagation among themselves. Nature produces individuals, declares Charles E. Bessie, and nothing more. She produces them in such countless numbers that we are compelled to sort them into kinds in order that we may be able to carry them in our minds. This sorting is classification taxonomy, but right here we are in danger of misunderstanding the matter. We do not actually sort out our individuals. We imagine them sorted out. It is only to a very slight extent that the systematic botanist ever actually sorts out individuals. So species have no actual existence in nature. They are mental concepts and nothing more. They are conceived in order to save ourselves the labour of thinking in terms of individuals, and they must be so framed that they do save us labour. It should be borne in mind, ably summarises Asa Gray, that the natural system of botany is natural only in the constitution of its genera, tribes, orders, etc., and in its grand divisions, that its cohorts and the like are as yet only tentative groupings, and that the putting together of any or all these parts in a system, and especially in a lineal order necessary as a lineal arrangement is, must needs be largely artificial. So that even the best perfected arrangements must always fail to give of themselves more than an imperfect and considerably distorted reflection of the plan of the vegetable kingdom, or even of our knowledge of it. End of section 19. Section 20 of The Science History of the Universe, Volume 6. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. The Science History of the Universe, Volume 6, edited by Francis Rolt Wheeler. Botany. Chapter 2. Plant Structures. The work of the earlier botanists was given over to two main objects, the classification of species and varieties in a manner that should most readily account for the entire system, and the determination of a true basis for such a taxonomic classification, requiring a somewhat close study of the morphology and the physiology of the plant. The later botanists, beginning mainly from the bases laid down by Linnaeus, developed the science of botany into a study of no little complexity, and questions arose of intense interest in themselves, but which took for granted a basic knowledge of these simpler matters of structure and of classification. As it would be difficult to carry the development of botanical thought up to its modern complexity without an assurance that the reader was conversant with the general outline, it is thought wiser to touch on it briefly here. Plants are differentiated from each other by certain variances of their parts, which again reveal causes deeper still. Wherefore, an understanding of the nature of these parts should precede a statement of their differences. Just as the man has various members by which he sees, hears, feels, so have the plants several kinds of organs. The advantage of this to the plant becomes plain by using the common illustration of the difference between a tribe of savages and a civilized community. Several kinds of organs in a plant mean to the plant just what division of labor means to the community. It results in better work and more work. All the work done by plants comes under two heads, nutrition and reproduction. This means that every plant must care for two things. One, the support of its own body, nutrition, and two, the production of other plants like itself, reproduction. To the great work of nutrition, many kinds of work contribute, and the same is true of reproduction. In a complex plant, therefore, there are certain organs which specially contribute to the work of nutrition, and others which are specially concerned with the work of reproduction. The plant is extremely dependent upon its surroundings, more so because of its lack of locomotion. For example, it must receive material from the outside and get rid of waste material. Therefore, organs must establish certain definite relations with things outside of themselves before they can work effectively, and these necessary relations are known as life relations. For example, green leaves are definitely related to light. They cannot do their peculiar work without it. Many roots must be related to the soil. Certain plants are related to abundant water. Some plants, such as parasites, are related to other plants. Each organ, therefore, must become adjusted to a complete set of relations, and a plant with several organs has many delicate adjustments to care for. Three conspicuous organs, root, stem, and leaf, are concerned with nutrition, and most of these plants have at some time also another structure, the flower, which is concerned with reproduction. On examining an ordinary leaf, the blade is seen to consist of a green substance through which a network of veins is distributed. The larger veins that enter the blade send off smaller veinlets that are invisible. This is plainly shown by a skeleton leaf, wherein it appears that the vein system, or the nation of leaves, is exceedingly diverse, although all forms can be referred to a few general plans. In some leaves, a single, very prominent vein, known as the midrib, runs through the middle of the blade. From this, all the minor veins arise as branches, and such a leaf is said to be penately veined. In other leaves, several large veins, ribs, of equal prominence, enter the blade and diverge, each giving rise to smaller branches. Such a leaf is said to be palmately veined. In still other leaves, all the visible veins run approximately parallel from the base of the blade to its apex. Such leaves being parallel veined, as distinct from the two preceding, which are both net veined. The upper and the under surface of a leaf is covered by a delicate transparent skin, epidermis, which generally shows no green color. Examined under the compound microscope, says John M. Colter, it is seen to be made up of small units of structure known as cells. Each cell is bounded by a wall, and in the epidermis, these cells fit closely together, sometimes dovetailing with one another. Characteristic openings in the epidermis also will be discovered, sometimes in very great numbers. The whole apparatus is known as a stoma. These numerous openings are the stomata, which give passageway into the interior of the leaf, putting the internal cells into communication with the air outside, and so facilitating the interchange of gases. The size of these apertures may vary under different conditions. Between these two epidermal layers is the massive green tissue making up the body of the leaf, and known as mesophyll. This comprises cells containing the numerous small green bodies, chloroplasts, that give color to the whole leaf. Usually the mesophyll cells are arranged differently in the upper and lower regions of the horizontal leaf. In the upper region, the cells just beneath the epidermis are elongated at right angles to the surface of the leaf, and stand in close contact forming the palisade tissue. In the lower region of the leaf, the cells are irregular in form, and so loosely arranged as to leave airspace between the cells, the whole region forming the spongy tissue. The airspaces communicate with one another, thus forming a labyrinthine system of air chambers throughout the spongy mesophyll. It is into this system of air chambers that the stomata open, and thus what may be called an internal atmosphere is in contact with all the green working cells, and this internal atmosphere is in free communication through the stomata with the external atmosphere. In general, says G. F. Atkinson, the function of the foliage leaf as an organ of the plant is fivefold. One, that of carbon dioxide assimilation. Two, that of transpiration. Three, that of the synthesis of other organic compounds. Four, that of respiration. Five, that of assimilation proper or the making of new living substances. The importance of the work of leaves is apparent, but this work cannot be done unless the leaf is exposed to light. This fact explains many things in connection with the position and arrangement of leaves. Leaves must be arranged to receive as much light as possible to help in their work. But too intense light is dangerous. Hence, the adjustment to light is a delicate one. If green plants should stop the manufacture of carbohydrates, the food supply of the world would soon be exhausted. All other forms of food are derived from carbohydrates in some way, and only green plants can add to the stock that is being drawn upon continually. This means that green plants must manufacture carbohydrates not only for their own use, but also for the use of animals, and of plants that are not green. Since leaves are chiefly expansions of green tissue, they are conspicuous in the manufacture of carbohydrates. It must be remembered that the manufacture goes on wherever there is green tissue, whether it is found in leaves or not. A very conspicuous fact about this manufacture is that it cannot go on unless the green tissue is exposed to light. This explains why leaves are adjusted in so many ways to obtain light. It also gives name to the process, photosynthesis, the name indicating that the work is done in the presence of light. The process demands that carbohydrates shall be made from raw materials common in nature and easily obtained by plants, and in photosynthesis two such substances are used. One of these is water, which in the plants commonly thought of is absorbed by the roots from the soil. The other substance is carbon dioxide, a gas present in small proportion in the air, really in the form of carbonic acid gas, but one which is being constantly renewed as it is used, so that it is always available. Water is made up of one part of oxygen and two parts of hydrogen, while carbon dioxide consists of two parts of oxygen and one part of carbon. These are just the elements that enter into the structure of a carbohydrate. In photosynthesis the elements of water and carbon dioxide are separated and recombine to form a carbohydrate, and in this process oxygen is a waste product and is given off by the working cells. Therefore in the sunlight a leaf is absorbing carbon dioxide and giving off oxygen, and this gas exchange is the superficial indication that photosynthesis is going on. Such an important organ as the leaf says Coulter again, with its delicate active cells necessarily in communication with the air is exposed to numerous dangers. Conspicuous among these dangers are drought, intense light, and cold. Perhaps the most common danger to most plants is an excessive loss of water, and when a drought prevails the problem of checking transpiration is a most serious one. As the leaves are the prominent transpiring organs, the chief methods of protection concern them. The epidermis may be regarded as an ever-present check against transpiration, for without it the active mesophyll cells would soon lose all their water. In some plants of very dry regions what may be regarded as several epidermal layers appear. The cuticle which is often developed upon the epidermis is one of the best protections against loss of water. It is developed by the exposed walls of the epidermal cells, and being constantly renewed from beneath, it may become very thick and many layered. In dry regions or in any much exposed place the cuticle is a very constant feature of plants. In many leaves remarks Atkinson certain of the cells of the epidermis grow out into the form of hairs or scales. They may form only a slightly downy covering, or the leaf may be covered by a woolly or felt like mass so that the epidermis is entirely concealed. In dry or cold regions the hairy covering of leaves is very noticeable, often giving them a brilliant silky white or bronze look. In dry regions each leaf endeavors to expose as small a surface in proportion to substance to the drying air and intense light. That this reduction in size holds a direct relation to the dry conditions is evident from the fact that the same plant often produces small leaves in a dry region and larger ones in moist conditions. In the case of the cactus a large group in the dry regions of the southwest the leaves have become so much reduced that they are no longer used in photosynthesis and this process is carried on by the green tissue of the globular cylindrical or flattened stems. The rosette habit is a very common method of protection used by small plants growing in exposed situations as bare rocks and sandy ground. The clustered overlapping leaves form a very effective arrangement for resisting intense light or drought. There are leaves which can shift their positions according to their needs directing their flat surfaces toward the light or more or less inclining them. Such leaves have been developed most extensively in the great family to which peas and beans belong, the most conspicuous ones being those of the so-called sensitive plants. The name has been given because the leaves respond to various external influences by changing position with remarkable rapidity. A slight touch or even jarring will call forth a response from the leaves and the sudden application of heat gives striking results. Insect devouring plants usually grow in swampy regions the leaves forming small rosettes upon the ground. In one form of sundew the blade is round and the margin is beset by prominent bristle-like hairs each with a globular gland at its tip. Shorter gland bearing hairs are scattered also over the inner surface of the blade. All these glands excrete a clear sticky fluid which hangs to them like dew drops and which not being dissipated by sunlight has suggested the name sundew. If a small insect becomes entangled in one of the sticky drops the hair begins to curve inward and presently presses its victim down upon the surface of the blade. The famous venus fly trap is found only in certain sandy swamps in North Carolina. The leaf blade is constructed so as to work like a steel trap. The two halves snapping together and the marginal bristles interlocking. A few sensitive hairs like feelers are developed on the leaf surface and when one of these is touched by a small flying or hovering insect the trap snaps shut and the insect is caught. Only after digestion which is a slow process does the trap open again. The stem is distinguished as that part of the plant which bears the leaves. It has for its chief function says C. C. Curtis the production and display of the leaves and roots and the conduction of the materials which these organs are especially concerned in handling. It serves as a connection between them, carrying up the material absorbed by the roots and distributing the various substances received from the leaf. The stem may be compared to a system of transportation carrying building material for new cells and arranging for the bearing away of that which is waste. The stem best adapted for the proper display of leaves is generally upright for they can be spread out on all sides and carried upward toward the light. To maintain the erect position is not a simple mechanical problem and in large woody stems it involves an extensive development and arrangement of supporting tissues. Other stems lie along the ground bearing leaves only on the free side while a third great group is that of the climbers which use other plants as supports. The greatly honest of South America belong to this class. It has been shown that the stem is in a sense a transportation system and it becomes immediately evident that the material transported must be largely insoluble form. This liquid is known as sap. It is important to notice says J. Y. Bergen and C. M. Davis in their principles of botany that sap is by no means the same substance everywhere and at all times as it first makes its way by osmotic action inward through the root hairs of the growing plant it differs little from ordinary well water. The liquid which flows from the cut stem of a tree just before the buds have begun to burst in the spring is mainly water often with a little dissolved organic acids proteides and sugar. The sap which is obtained from maple trees in late winter or early spring is far richer in nutritious material while the elaborated sap which is sent so abundantly into the ear of the corn at the time of its filling out contains great stores of food to support plant or animal life. Most root forms are adapted for growth in the soil but there are many of which this is not true thus many of the orchids have aerial roots which fasten the plants to the branch of a tree and absorb moisture from the heavy humid air of a tropical forest others are adventitious like the ivy which caused the plant to cling to a wall others again like the mistletoe and the daughter are parasitic and are adapted to prey upon their host while another large group of roots are adapted to life in the water such as the duckweed. The length of roots is rarely realized thus winter wheat has been found to extend to a depth of seven feet and the average root stretch of a plant of common oats is 154 feet the mexican mesquite has been known to extend 60 feet below ground in the search for water the growing tip of each root and rootlet is protected by a cap of cells called the root cap this root cap consists of several layers of cells the outer ones gradually dying or being worn away as the tip of the root pushes through the soil and being replaced by new layers which are continually forming beneath a short distance behind the root cap the surface of the root becomes covered by a more or less dense growth of hairs known as root hairs these hairs are out gross sometimes very long ones from the superficial cells a single cell producing a single root hair in fact the root hair is only an extended part of the superficial cell the root absorbs water and materials dissolved in it from the soil and the root hairs enormously increase the absorbing surface thousands may occur on a square inch of surface in the center of a young root is a solid vascular cylinder often called the central axis sometimes enclosing pith investing the solid vascular cylinder of the root is the cortex which often can be stripped from the central axis like a spongy bark the wood xylem and the baste phloem of the vascular cylinder do not hold the same relation to each other as in the stem the vascular cylinder instead of being made up of vascular bundles with wood toward the center and baste toward the outside as in stems is made up of wood and baste strands alternating with each other around the center the wood strands radiate from the center like the spokes of a wheel and the baste strands are between these spokes near their outer ends this arrangement of wood and baste is peculiar to roots the vascular bundles of the root connect with those of the stem and these in turn with those of the leaves so that throughout the whole plant there is a continuous vascular system end of section 20 section 21 of the science history of the universe volume six this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Melanie Young the science history of the universe volume six edited by Francis Rottweiler botany chapter three reproduction structures the root the stem and the leaf being the three principal organs in the nutrition of a plant the matter next of importance is a consideration of the manner of its reproduction usually this is popularly supposed to be by a flower but a large division of plants are flowerless and reproduce in many diverse ways as moreover the mode of reproduction often constitutes a means of differentiating between various species it will be treated therein but certain main principles may be laid down thus the earliest form of reproduction is that of mere cell division which cell so far as can be seen is not marked out from other cells indeed all the cells are capable of division capable of division next comes the setting aside of a certain cell which is called a spore and what seems strange in the vegetable world certain of these by the lashing about of filaments are able to swim and are called swimming spores so far all has been without sex and is called asexual but still very early in the plant kingdom two cells very like the swimming spores yet different in action are produced which are called gametes these have an affinity for each other come together fuse or fertilize and thus fertilized are called zago spores and from these are thrown off spores which can produce new plants these two gametes at first are very similar but in higher forms become strongly dissimilar and are called sperms and eggs the organ producing the sperms is called the antheridium that producing the egg is known as the oogonium instill higher types the archegonium the last stage in this type of reproductive process is that in which different plants sometimes different stems produce sex organs which may be termed respectively male and female the highest and the vast division of the plant kingdom known as spermatophytes or seed bearing is so called because of its development of seeds and reproduction thereby the gymnosperms of which pine trees are the best known produce no flowers but the angiosperms have the sexual system very fully developed in the flower a flower is a highly modified stem peculiarly adapted for perpetuation the stem like nature of the flower is very noticeable before it opens at which time a series of leaves protects the delicate parts within these green leaves are known as the calyx each leaf of which is separately distinguished as a sepal as the bud opens says Curtis a number of organs are disclosed particularly noticeable are a set of variously colored leaves known as the corolla each leaf of which is called a petal within the perianth which is the calyx and corolla together are two kinds of organs the pistols and the stamens collectively known as sporophylls since their special work is to produce certain cells called spores the anthers discharge pollen which is carried in various ways to the pistol where the ovules are situated it is by the fertilization of the female nucleus of the egg cell at the apex of the embryo sac in the pistol by the male nucleus from a pollen grain that plants arise the transfer of the pollen to the pistol this transfer i.e pollination is affected in many angiosperms by insects although in some cases the wind serves to carry pollen as it does in the gymnosperms this mutually helpful relation between flowers and insects in some cases has become so intimate that they can not exist without each other flowers are modified in many ways in relation to insect visits and insects are variously adapted to flowers the pollen colder points out may be transferred to the stigma of its own flower self-pollination or of some other flower of the same kind cross pollination in the latter case the two flowers concerned may be upon the same plant or upon different plants which may be quite distant from one another since flowers are very commonly arranged to secure cross pollination it must be more advantageous in general than self-pollination the advantage of this relation to the insect is to secure food this the flower provides in the form of either nectar or pollen and insects visiting flowers may be grouped as nectar feeders represented by moths and butterflies and pollen feeders represented by the numerous bees and wasp the presence of these supplies of food in the flower is made known to the insect by the display of color by odor or by form moreover the flower not only must secure the visits of suitable insects but also must guard against the depredations of unsuitable ones cross pollinating flowers may be illustrated under three heads distinguished from one another by their methods of hindering self-pollination but it must be understood that almost every kind of flower has its own way of solving the problems of pollination the following illustration will serve to show one of the processes that depended upon position in this case the pollen and the stigma are ready at the same time but their position in reference to each other or in reference to some confirmation of the flower makes it unlikely that pollen will fall upon the stigma in the family leguminosa to which the pea being etc. belong the several stamens and the single carpal are in a cluster enclosed in a boat-shaped structure or keel formed by two of the petals the stigma is at the summit of the style and projects somewhat beyond the pollen sacks some of whose pollen lodges on a hairy zone on the style below the stigma while the stigma is not altogether secure from receiving some pollen the position does not favor it the projecting keel is the natural landing place for a bee visiting the flower and it is so inserted that the weight of the insect depresses it and the stigma comes in contact with its body not only does the stigma strike the body but by the glancing below the surface of the style is rubbed against the insect and upon this style below the stigma the pollen has been shut and is rubbed off against the insect at the next flower visited the stigma is likely to strike the pollen obtained from the previous flower and the style will deposit a new supply of pollen but in the general flower as visited by the insect the pollen grains that reach the stigma the specially prepared surface for receiving them begin to put out pollen tubes these tubes grow through the stigma and enter the style grow down the style and enter the cavity of the ovary reach the ovules and enter their micro piles and finally penetrate the ovule to the egg throughout this progress of the tube the male cells are in its tip and when the egg is reached they are discharged from the tube and one of them fuses with the egg this is the act of fertilization and through it the egg becomes an oospore an important difference between gemnosperms and angiosperms should be noted here in gemnosperms the pollen reaches the ovules for they are exposed but in angiosperms the pollen reaches only the surface or stigma of the pistol that encloses the ovules the oospore lying in the midst of the ovule at once begins to germinate and forms a young plant or embryo when the embryo is forming the ovule develops a hard coat outside and a seed is the result the seed coats are varied in many ways as in the pea and the brazil nut but their internal anatomy follows the same general pattern and they nearly all contain food for the embryonic plant it is this food in grains and in nuts which is used as food stuff by man the three kinds of food stored in seeds are starch oil and the albuminus substances called proteins the young seedling does not push its way straight out of ground but sends up an arched part of the stem known as the hypochotal and when the surface of the ground is broken the stem straightens and the cotyledons appear the lower elongating tip of the hypochotal directs its growth downward that is toward the earth even if it has to curve about the seed to do so it is exceedingly sensitive to surrounding influences a condition that is called irritability especially so to gravity a condition that is called geotropism the root being said to be geotropic if the same stimulus and response that directs the root tip toward the soil continues to direct it within the soil it continues to grow directly downward and becomes a tap root when such a root having entered the soil begins to send out branches these do not respond to the stimulus of gravity as does the tap root where they extend through the soil in every direction it is likewise sensitive to light the stem being attracted and the root repelled with the establishment of roots in the soil and the exposure of green leaves to the light and air germination is over for the plant is able to make its own food end of section 21 recording by melanie young