 So I think it's about time you started. So you recall last time we started talking about some of the differences between flowering plants and other seed plants we'd seen earlier that might, at least part, be responsible for their success, like the ovary that protects the ovules and mechanisms promoting out-crossing. And then I started talking about some of these pollination syndromes that reflect adaptation with particular groups of pollinators. We talked about bee pollination, the most important biotic pollination, moths, butterflies, birds, and bats. And I just want to wrap that up before getting into some of the innovations of the angiosperm lifecycle that are really important to consider in terms of the success of angiosperms. And then we'll talk about fruits and seed germination to wrap up this overview of diversity in the course. And then starting next time, we'll be getting more into the anatomy and structure of plants and how that affects their ability to grow and transport nutrients and water, et cetera. So some really different types of adaptations and things you've seen in animals. All right, so I just briefly talked about fly pollination at the end of last lecture as another example of deceit pollination. Remember, in pollination, it's often a mutualism where the plant offers a reward to the pollinator that benefits in some tangible way, often generally food. The plant, of course, benefits by being pollinated. But in fly pollination, like in those bee orchids, the pollinator loses. But it's still effective. The fly pollination syndrome is associated with reddish or maroon-colored inflorescences or flowers that, as I mentioned, are light-spotted, which sort of resembles maggots growing on rotting meat. And they often have a fleshy texture, I mean, a definite fleshy texture compared to most flowers that can fool flies into thinking they're walking around on rotting meat. And in the process, pollinate the plants. And the floral scents are incredibly similar to cadavers, which has led to a lot of these plants' flowers being called corpse flowers, which both of these are, even though this is an inflorescence, not an individual flower. And so the female flies visit these flowers and lay their eggs. And then the eggs hatch and the maggots die. They starve to death because there's no food here for them. So this is real deceit pollination. But fortunately for the plants and the flies, there are a lot of flies to go around. So there's no loss of the pollinator through time. And one of the neat things about fly pollination is it's associated with some of these absolutely huge inflorescences and flowers. And I mentioned last time the Titanarum, which is actually in cultivation up at the UC Botanical Garden. And when it flowers, it's advertised on the Berkeley homepage and definitely worth checking out. It gets up to 10 feet tall, the inflorescence, an immense thing. It's native to the rainforests of Indonesia, which happens to be where you also find this plant, which is distantly related. It's a case of convergent evolution on fly pollination. The name is riflesia arnulzii. The name's not that important at all. But it's an individual flower. And it's the largest flower known on Earth. It gets up to about a meter in diameter. And it weighs in at over 20 pounds. So it's a huge flower. And it's not only cheating flies in the process of getting pollinated, but it's also parasitizing another flowering plant for all of its nutrients. This thing is a holo parasite. It has no stems, leaves, true roots. It's just growing inside the tissues of a member of the grape family. So you can't even tell it's there until it flowers. And this gigantic flower emerges. It's pretty bizarre. OK, so wind pollination also occurs in angiosperms. And remember, this is the dominant type of pollination in gymnast berms, except for cycads. And it's secondarily evolved, we know now, from insect pollination or animal pollination. It occurs in about 20% of all flowering plants, so not an insignificant number, given there are like 300,000 flowering plants. And it used to be thought that these wind pollinated flowering plants mostly constituted a single group, a natural group. But it turns out that's not true. Things like oaks, birches, beaches, hazelnuts shown here are not closely related to things like mulberries and stinging nettles and marijuana, which are a separate origin of wind pollination. And there's some other examples too. But they've all evolved, or not every case, but there's a suite of features that they've converged on evolutionarily that make them appear very similar. So it's a really great case where we have multiple origins of a type of pollination, where a whole suite of features comes along with that, that pretty clearly are important adaptations to that type of pollination. So one thing is that the flowers are either pistolade or staminate, but not both. So that has some obvious advantages in terms of preventing self-pollination. And often, the pistolade and staminate flowers are born in separate inflorescences, sometimes on separate plants, also promoting out-crossing. And the petals, not surprisingly, are really small or altogether absent. And that makes sense both in terms of investment. Why invest in a big, attractive set of display features when you're not trying to attract an animal pollinator anymore, but also it's a real disadvantage to have big, showy petals if you're wind pollinated, because they're just gonna get in the way of the pollen being dispersed and received. So it's to the advantage of the plant to not have these inert surfaces around that can block pollen. And that's also the case about their flowering time. So in many cases, not all cases, but in many cases, especially when we have deciduous taxa involved, which many of these are, a lot of our hardwoods fall into this category, wind pollination, that are winter deciduous. They'll flower before the leaves expand in the springtime, and that's an advantage in terms of minimizing blockage of pollen by these inert surfaces. And also the antlers, like in a lot of cases where we have dispersal from sporangia, as well as micro-sporangia and gymnosperms, the antlers open in dry weather which promotes dispersal of pollen. And they tend to have in large stigmatic surfaces. This is really common, like in grasses and other groups where you get these feathery looking stigmas that maximize surface area to capture pollen. So that's a common feature. And also when you look at the pollen itself, it's really different from the insect pollinated or animal pollinated flowers where the pollen comes in clumps and it's sticky or oily and ornamented. Here you can see it's dry and it's smooth walled. It's dispersed in a single grains which maximizes buoyancy in the air. So there's a lot of these great features that wind pollinated plants have evolved. And they can get their pollen around really well. Some wind pollinated plants can disperse pollen over large distances and to the misfortune, a lot of us that have hay fever, pollen allergies. And there's also even water pollination. This is really rare, but there are some angiosperms that have gone back to an aquatic environment. Ancestrally, these were land plants, but some angiosperms have become aquatic, both in freshwater and in marine situations. And this is one of them, valesnaria, which is the ribbonweed. And some of these have, there's a bunch of different adaptations to pollination in these different groups of plants that have gone back to water. But in valesnaria, you have the release of the male flowers. It actually just pops the male flowers off of the pedestal and they float up to the top and they float around on the surface. The female flowers are held with some tension so that there's actually a depression in the water surface and the male flowers floating around will be drawn into the depression and the water surface and pollinate the female flower, or the, I should say the pistolate flowers. So in the eel grasses, which I should say ribbon grasses are not really grasses, they are monocots, just in case you're interested. Eel grasses, which you can see out in estuaries along the coast here and even out in the open ocean, are our only local group of marine angiosperms and they're also not really grasses, but they are monocots. And they actually release their pollen underwater. Pollen is usually really vulnerable to wetting. If pollen gets wet, it's usually curtains, but in the case of eel grasses, they can withstand immersion in salt water and it's thread-like pollen that is carried around in the currents and will wrap around the stigma when it comes into contact and germinate. So there's a bunch of really amazing adaptations of flowering plants to pollination, specializations involving both abiotic and biotic agents. Okay, so any questions about pollination before we move on? All right, so I just wanna talk briefly about some evolutionary trends that we see in flowering plant, flower evolution. There's a number of things that come up repeatedly across flowering plants. One of them is the loss or reduction in number of floral parts. So if we look at some of these flowering plants that reconstruct this having fairly ancestral flowers, they usually have a large and indefinite number of parts of the different orals or different groups, perianthrope, sepals, petals, stamens and carpals, but we tend to see a general reduction through time, this is a red maple where it's lost the functional pistols in these particular flowers. There are some flowers on these plants that can be bisexual and they readily self, but we see, this is a particular species where we see a trend toward diacy occurring during this snapshot in time. So it's kind of an interesting species in that regard. Also I mentioned in wind pollinated plants you can have loss of the petals altogether. There are various specializations that have resulted in loss of floral parts and it's rare that we see an amplification in number of floral parts, although it can happen. Another thing that we see is fusion of parts of both the same type, like petals to petals, in the case of this fox glove here, where all the petals are fused together into this tubular corolla. That's a common thing. We can also get fusion of unlike parts, for example, stamens fused to the inside of petals and that's what's going on inside the flower here. You can't see it, but that sort of fusion of like parts and unlike parts can help to integrate the flower in a way that it functions as a whole very effectively during pollination and can allow for more precise, accurate placement of pollen on a pollinator. So for example, a pollinator lands in the throat of this flower and depresses that lower lip and that's gonna cause the stamens above to come down on top of the back of the pollinator and deposit pollen or the stigma to come down and pick up pollen. So that can go hand in hand with reduction in number of parts because if you have more accuracy and precision in your pollen placement and pollen removal, you don't need necessarily, for example, as many stamens. So these kinds of, these trends can go together in some cases. Another trend that we see is a shift from radial symmetry where we have basically like a pie where you can cut it in any direction and get two equal halves, radial symmetry, as opposed to bilateral symmetry like us where you can only cut us in half in one plane and get two equal halves. And that's what we see in this fox glove as well as in this orchid where that's the only plane in which we could cut this flower and get two equal halves. And we get this bilateral symmetry evolving in a lot of different groups of flowering plants and it often goes along really well with specialization in pollinator, in pollination with particular pollinators. So it also promotes precision and accuracy of pollen placement and in the case of orchids, most orchids only have a single stamen. So they've gone down to a single stamen and they transfer all their pollen at once with that single stamen. So that's a repeated trend in these groups that show bilateral symmetry of flowers have significantly higher diversity than groups that don't. That's been shown in a number, there's enough different plant families where that's evolved that it's been, we can do comparative studies and make a rigorous case for an increased diversity when you evolve this kind of specialization. And another trend that we see happening over and over again is additional protection of the ovaries, of the ovules. And remember the ovules are already contained within an ovary in flowering plants unlike in gymnast berms, which provides some protection from herbivores, from drying out with regard to abiotic factors, et cetera. And in some flowering plants, other floral whorls like the periant, the petals and sepals, the bases of the stamens can form a floral tube that fuses around the ovary, or the ovary can actually become embedded in the tip of the stem like in a cactus here. We can have tissue in addition to the ovary fused around and protecting the ovules. So the ovaries, what we call inferior in this case, because it looks like it's actually depressed down into the stem, which it actually is in cacti, but in most plants that have an inferior ovary, it's the other outside parts of the flower that fuse around the ovary. That those are just details, but the main point is that there's other tissue in addition to ovary tissue that surrounds the ovules, is fused to the ovaries, to the ovary. And you only get a single ovary in cases like that. Okay, so now the life cycle of angiosperms is pretty similar to the gymnast sperms, the other seed plants, but there's some really important differences that make a lot of sense in terms of how these might have been beneficial to success of angiosperms. So let's look at the pollen development first. And this is a diagram from your textbook. And just like in the gymnast sperms, we have a microspore genesis. We have microspores formed in microsperangia, which through meiosis, these are pollen sacs, as we call them, but they're microsperangia. And here you can see the four products of meiosis. And the male gametophyte then, of course, the microspore germinates undergoes mitotic divisions, already haploid, like any other spore, and the gametophytes haploid. But at the time of dispersal, the male gametophyte usually consists of only two cells, a tube cell that will direct the growth of the pollen tube and a generative cell that will undergo another mitotic division to produce two sperm cells. But this is the bare minimum number of cells that this male gametophyte needs to function properly. It has to have a tube cell in order to produce the pollen tube to grow down through the style and reach the ovules in the ovary. And it needs both of those sperm cells. Okay, unlike in the gymnast sperms, it only need one of their sperm cells. The angiosperms need both of the sperm cells of the male gametophyte, and we'll get into that in a minute. That's another important innovation we'll get to. Okay, but first let's talk about the female gametophyte. Remember in the gymnast sperms, the female gametophyte is a fairly, it takes up the majority of the seed and is the main nutritive tissue for the developing embryo after fertilization of the egg. So in the case of the flowering plants, the female gametophyte, it's not this large multicellular gametophyte, I said large, relatively speaking, but more cells than you'd care to count. That's for sure. In the case of the gymnast sperm female gametophyte, and the presence usually of multiple archegonia in the gymnast sperm female gametophyte, remember where the eggs are found. But in the female gametophyte of angiosperms, the mature female gametophyte only consists usually of about seven cells and eight nuclei. One of the cells, the central cell, the largest has two nuclei, what are called the polar nuclei. But here you can see the opening in the ovule here where the pollen tube will enter. And there's very little to this female gametophyte. There are three cells up at the back end of the ovule, the antipodal so-called, these two polar nuclei in the big central cell. And here's the egg, again, close to the opening in the ovule, the micropillar end. And it's flanked by two individual cells, one on either side that are called synergids. Not important, but these may be the vestiges of an archegonium, but there's really no clear archegonium present, no gametangium sac that contains the gametes. Just like in the pollen, they've lost the gametangium. So the angiosperms don't have either female or male gametangia in their gametophytes. So this is a really stripped down female gametophyte and a super stripped down male gametophyte as well in the angiosperms. So a pretty minor investment here compared to what the gymnasperms make in their gametophytes. All right, so fertilization, we talked about pollination last time of angiosperms where the pollen's deposited not on the ovule itself, like in gymnasperms, but at the stigmatic area on the stigma. And we talked about how the pollen tubes have to grow down through the style to reach the ovules. And once that occurs, the pollen tubes grow in through the micropillar end as they do in gymnasperms. And we have fertilization of the egg by one of the sperm cells. And there's never any flagellae on the, I think I already mentioned there's no flagellum on the sperm and angiosperms. They're delivered right to the female gametophyte by the pollen tube. So that's nothing new in terms of a zygote being formed. But the other sperm, the second sperm produced by the pollen tube also undergoes fusion, not with the egg, but with those two polar nuclei in the central cell. And so you end up with this triploid nucleus. And this will now undergo a lot of free nuclear divisions without the formation of cell membranes and cell walls separating them from one another initially. And then it'll start walling off those nuclei. So we go from this milky endosperm to a cellular endosperm. Now the significance of this, so what happens is after the zygote forms and this endosperm forms, we start getting a lot of activity of this endosperm tissue. It starts rapidly developing really before the zygote's doing anything. So we're investing in what becomes the nutritive tissue. The endosperm becomes the nutritive tissue for the embryo, the developing embryo. So the important thing to consider here is that in the gymnospherms, there's this huge investment in the female gametophyte, this very large organism inside the seed relative to the size of the female gametophyte in angiosperms. But in the case of, but if it doesn't get, egg doesn't get fertilized in a gymnospherm, all that investment is a big waste of resources for the parent sporophyte that produce those ovules. Because that female gametophyte in the gymnospherm is parasitic on the sporophyte that gave birth to it. So that's a potential problem in terms of wastage that angiosperms get around by waiting to invest in the nutritive tissue for their developing embryos until after fertilization happens. So angiosperms wait and then start developing the nutritive tissue, this endosperm. And if you've ever broken open a coconut, which coconuts have the world's largest seed, so this is easy to see, the milk inside the coconut is the acellular endosperm. So that's the free nuclei floating inside a plasm where we haven't yet had cell walls formed. Whereas the meat of the coconut that lines the inside of the seed, that's the cellular endosperm that where we have had cell membranes and cell walls partitioned off the nuclei. And the embryo is really just a tiny little thing that you have to break open. You have to dig around in the cellular endosperm to locate. So that's give you a little bit of context for endosperm. So any questions about double fertilization then? Okay, so in the end then an angiosperm seed, that's a good question. Yeah, well that's exactly what we're gonna get to right now. It's really unclear to be frank about it in terms of whether the triploidy of those nuclei has any nutritive benefit to the embryo or not. But it is still a clear difference between what you see in an angiosperm seed versus a gymnast sperm seed. Here's a cartoon of an angiosperm seed. Again, we have this diploid embryo, the young sporophyte. We have the triploid endosperm that forms the nutritive tissue from developed after fertilization with that second sperm fusing to the polar nuclei. And then we have diploid seed coat tissue from the integument that was produced around the ovule by the parent sporophyte that made the ovule. And in contrast, in the gymnast sperm, we have basically the same arrangement except for the nutritive tissue here as haploid. It's female gametophyte tissue. Whereas the female gametophyte's relatively insignificant in terms of its nutritive value to the embryo compared to the endosperm, okay? So this investment was made before fertilization. This investment was made after fertilization and that nutritive tissue. All right, so another innovation that may help to explain success of angiosperms in part is the evolution of fruit. And we've talked about fruiting bodies in mushrooms, but that's shorthand. Strictly botanically speaking, the only real fruit is produced by angiosperms. And fruit has real value to angiosperms in terms of promoting dispersal of seeds. So we talked about these different pollination specializations, these different pollination syndromes, for example, that promote dispersal of pollen, which is one way in which angiosperms can get their genes around is by moving around the male gametophytes, which are mobile, relative to the rest of the life cycle. The other stage of the life cycle that's mobile are the seeds. And so fruit is an innovation of angiosperms that promotes dispersal of seeds. And basically speaking, a fruit in its strictest sense is just a ripened ovary. So remember, the ovary is the base of the pistol, the chamber in which the seed or the ovule or ovules are located. And at maturity, the ripened ovary becomes all or part of the fruit. Sometimes there are additional tissues that make up the dispersal unit, the fruit. Sometimes the fruit isn't the dispersal unit, but it is still the ripened ovary, and we'll get to that in a second. That is, angiosperms can directly release their seeds, and the seeds can be dispersal units, but often the fruit is the dispersal unit containing the seeds. So there's a lot of classification that has revolved around describing different types of fruits. And the important thing to realize here is that the classification of fruits is not a natural classification. That is, it doesn't reflect phylogeny. These different so-called types of fruits are convenient ways of classifying fruits that help to understand the morphology of the fruits, that in the anatomy of fruits, and can also be beneficial in understanding dispersal, but these different types of fruits have evolved multiple times in different groups of flowering plants. And the most widespread type of fruit in this three-type classification I'm gonna talk about here briefly. It's in your textbook, it's called a simple fruit, and a simple fruit's a good name for it because it simply is a fruit derived from one ovary. So it's basically derived from one ovary of one flower. That ovary might be from one carpal or from multiple carpals that were fused together into a compound pistol, but it's from one pistol regardless of whether that pistol is from one or more carpals fused together. And a cherry apricot, these are great examples of simple fruits that are fleshy fruits, obviously. Although the pit of the cherry, the pit of the apricot is also a fruit wall that protects the seed inside. There are different layers of fruit that can be really different from one another. And fruits can be de-hissant or inde-hissant. That is, fruits can open up at maturity and release the seeds directly, in which case the seed is generally the dispersal unit. Or the fruit can remain fused around the, or doesn't actually open by some sort of suture and surrounds the seeds, in which case the whole fruit is typically the dispersal unit along with the seeds. So another type of fruit then is an aggregate fruit, the second of these three major types that your book describes. And an aggregate fruit is something like a raspberry or a blackberry that is a fruit derived from more than one separate carpal of one flower. So separate pistols, each from one carpal, you can see are these little, each one of these little fruitlets that makes up a raspberry or blackberry is an individual pistol from one carpal that are, they're separate, but they're still basically part of a common dispersal unit here. The whole aggregate fruit is removed as a unit, typically by an animal and dispersed. So that's another type of fruit that still is from a single flower, but from multiple pistols. And another type of fruit is a multiple fruit. And a multiple fruit is a fruit derived from multiple flowers. And this is a case in the pineapple where you have clearly distinct flowers initially. I mean, they're obviously distinct at this point in their development. And then after we've had fertilization and seed development, the fruits developing here, and eventually all of these flowers coalesce together into one big dispersal unit, one large pineapple, where each of the little segments that you see, those little walled off units in the pineapple represent individual flowers of a common inflorescence of an entire array, compact array of flowers. Another great example of this kind of flower or this kind of fruit is a mulberry, which looks a lot superficially like a, something like a raspberry, but it's actually multiple flowers that make up that structure. And here again, the simple fruit, the aggregate fruit, a multiple fruit. Fruits can be either dry, they don't have to be fleshy. Fruits can be dry altogether, like a pea pod. At maturity, it dries out, splits open and releases the seeds. So fruit is just a mature ovary. It doesn't necessarily have to be the dispersal unit, but it often is. And even if it is the dispersal unit, it can be dry or fleshy. That we'll look at here in a minute. One last type of fruit to mention is this accessory fruit. And this is kind of a cool thing to think about because in accessory fruits, the ripened ovary is part of the fruit, but it's not the fleshy part. There's another fleshy part that's derived from other parts of either the flower or the inflorescence. And there are accessory fruits that fall in the category of simple, aggregate and multiple. So this is a, so simple aggregate and multiple fruits can also be accessory fruits. Or as I mentioned, the fruit has fleshy parts that are derived largely from tissues other than the ovary. And an apple is a great example of this. So here's the stalk of the apple flower where the flower was attached. And here's what's left of the sepals, the stamens and the styles of an apple. And you've no doubt seen those at the summit of an apple. So the ovary is right here. The ovary is the core of the apple, the papery part that you generally don't eat but throw aside. And the really juicy choice part of the apple, this outer part is accessory tissue. It's actually the floral tube formed from the bases of the sepals, petals and stamens that have fused together and fused around the ovary. So the ovary is inferior like we mentioned before. It's protected by this tissue. And dispersal agent coming and grabbing an apple or eating an apple is probably gonna be consuming mostly this external part in leaving the core and the seeds. So the accessory tissue is important and dispersal and it's not part of the ovary. The ovary can be spared from being eaten and the seeds as well but it can get moved away from the parent plant. The strawberries is another type of accessory fruit that's an aggregate and the little grainy inclusions on the outside of a strawberry, those are the ovaries. So the ovaries are a little dry into hissing fruits that we call akeens. The term's not important but they're not actually, they don't open at maturity. They contain a single seed each. And the actual fleshy part of a strawberry is the receptacle of the flower, which is basically the podium on which the other parts of the flower are born. And it's usually not an enlarged structure. It's pretty insignificant. We didn't even talk about it before. It's just the tip of the stem that the flower is born on but it becomes the fleshy part of the fruit that's the attractant for animal dispersal here. And here you can see the sepals. In a fig, the fleshy part of the fruit is basically the whole inflorescence. The fig inflorescence is like an inflorescence turned inside out. And all the fleshy, juicy part is mostly non-floral tissue, so it's the whole inflorescence. So there's a lot of innovation and diversity and fruit morphology. And in different groups of plants, they've gone in for very different kinds of ways of attracting pollinators and dispersing their seeds via different fruit innovations. And some of these are shown here. Now this is dispersal by wind and water, so non-animal dispersal. And there's a really wide range of adaptations of non-animal dispersal to wind and water dispersal or abiotic dispersal in angiosperms. And some of these are like in gymnast sperms where the fruit opens up at maturity and releases the seeds and the seeds might be winged or have a tuft of hair on them that makes them dispersable by wind, for example, like this winged gourd seed here. So similar to, say, a pine seed where the seed's the dispersal unit. But in other cases, the fruit is dispersed in the wind. For example, in a maple, there are wings on the fruit, this kind of fruit we call samara that blows in the wind. And in something like a dandelion, you've no doubt seen the fruits. The fruits are actually dry and de-hiscent structures that are attached to the sepals which are persistent and the sepals become parachute-like and carry the fruit along in the wind very buoyant. And in some plants, the entire plant is a wind dispersal unit like the tumbleweed where it breaks off at the base at maturity after it dries out. The outline of the whole plant is spherical and it just blows in the wind carrying all the fruits with it. So they're different units of dispersal from the smallest unit, the seed, to the entire plant. Cacti are another example where entire stems can be dispersed by impaling an animal's leg with the spines of the cactus and carrying the fruit along with it like in the so-called jumping choya down in our deserts here which are pretty dangerous to walk around for that reason. And also you can get dispersal by water. A lot of different tropical, especially plants, a lot of our island plants, if you go to the Hawaiian islands or Tahiti, some of the tropical islands, right along the edge of the water, you'll find a lot of plants that have dispersal adaptations to water which have buoyant fruits like the coconut and these fruits have hard seed layers or fruit layers that prevent the seed from being penetrated by saltwater until after dispersal. So this is another way in which plants can get around. So as I mentioned here, just as flowers have evolved in response to pollinators, fruits have evolved in response to dispersal agents. And so we have all of these mechanisms for dispersing pollen in pollination. We have all these mechanisms for dispersing seeds with the often involved fruit. So these are various important innovations of angiosperms. And as far as animal dispersal goes, there's a really wide diversity here as well. Some dry fruits are animal dispersed either intentionally like acorns, which can be picked up by squirrels or blue jays and carried some distance and cached. And then some proportion of those are forgotten about and they end up germinating. Some are carried long distances. Jays can fly between mountain ranges with acorns and they're carried inside and regurgitated when they get to a new area. Some are inadvertent like barbed fruits. And some of these are relatively painless in terms of just having say hooked prickles or something that attaches or sticky exudates that attach to the outside of fur or feathers and are carried from one place to another inadvertently. But others are more insidious. And the puncture vine has fruits that actually will puncture the feed of animals, including people if you're walking around barefoot in the desert and really nasty things that you have to take some effort to get out and presumably carried some distance sometimes before they're removed. Sometimes again, the seed is the dispersal unit. And like in the gourd I showed you that it's wind dispersed, sometimes the seed has some interesting innovations to promote dispersal that we don't see in gymnisperms, for example, like this little fleshy attachment to the seed here. The term's an Eliasome, you don't have to know that but it's a little edible body high in oil or protein that's attached to the seed and makes them attractive to ants which will carry them actively to their nests some distance away from the parent plant. They'll cash these seeds down their nests, they'll eat the food body and then they'll discard the seed or the seed will remain in the nest and eventually germinate. So there's some, this has evolved multiple times in different groups of plants. And then of course there are fleshy fruits that are or other or even dry fruits that are eaten directly and the fruit may be digested but the seed isn't. In fact the seed can be stimulated to germinate by the chemistry of the gut and then ends up in some fertilizer at the end of the process and germinates from that. So lots of great dispersal adaptations. And just one final note about fruit is that we probably all think we know what fruit is and what vegetables are. But these are all classified by US law as vegetables and you can see some things in here that are clearly fruits, tomatoes for example, peppers. These are ripened ovaries that contain seeds as you're all aware. But they're officially considered vegetables because they have savory rather than sweet flavor. And actually there was a case that was taken to the Supreme Court years ago by an importer who was bringing in tomatoes from outside the country and there was a tariff on vegetables at the time but not on fruit. And so he argued that I'm just bringing fruit and I'm not bringing in vegetables. I don't have to pay this tariff. And it went all the way to the Supreme Court and the Supreme Court ruled that yes, we agree that botanically the tomato is a fruit but we rule it officially by US law to be a vegetable. So the Supreme Court had the last word on it even though the botanist had to take a second place there but botanically speaking from this course's perspective at least we're gonna consider a fruit. All right, so angiosperm diversity as I mentioned, huge all over the world. We're still trying to understand how much diversity's out there and how it's related. How these different angiosperms are related to one another. And as I mentioned, how angiosperms are related to other seed plants, gymnast sperms is something that we haven't figured out. For a while we thought we had, in fact like 10 years ago when I was teaching my upper division systematics course, it was dogma that the angiosperms were the closest relatives of the Nita fights. Those things like the platypus of the plant kingdom that I showed you, the well witchia or the aphedra that produces that stimulant aphedrine. But now it's clear that those are actually more closely related to conifers than anything else. The Nita fights and the conifers are closely related. And we're not sure what the closest relatives of angiosperms are. But we do have a better idea about relationships among the major groups of angiosperms. And from high school biology, if you had any mention of flowering plants there, you probably heard about dicots versus monocots. These two major groups of flowering plants. Well it turns out that's sort of an artificial distinction is traditional distinction simplistic. And the monocots are a good monophyletic group and we'll get to their features in a moment. But that includes about a quarter of all flowering plants. So that's a huge diversity of flowering plants there. Includes the grasses and the grains. The dicots though are all these yellow lineages. And so they're not a monophyletic group, they're a perophyletic grade. And it looks like the presence of two cotyledonists or embryonic leaves is ancestral for flowering plants. And it's not a derived feature that diagnoses a monophyletic group. But there is one group called the eudicots that contains about two thirds of all angiosperm diversity. Two thirds of the recognized species. And remember, you means true. These are the true dicots as they're so-called now, even though these other lineages do have two cotyledons. And they're a nice monophyletic group. Together with the monocots, they make up the vast majority of all the flowering plants. These oldest living lineages here, which you know, well, you may have seen water lilies, which are among some of the early diverging lineages. But the others are obscure, mostly southern temperate groups in the southern hemisphere. That's only about a hundred species total there. And the magnolias and relatives, that's about 8,000 species, but the bulk of the 300,000 or so species are over here. And we're gonna focus on these for the rest of the course. Any questions about that? That's just sort of a general overview. Just wanna make it clear that the, why we're calling them eudicots rather than dicots as a whole, because this is the natural group of dicots that makes up most of them. So these are some of the features shared by most monocots and shared by most dicots. And in some cases, the feature is derived in the monocots. In some cases, or some cases, the features that distinguish them. And one of them's derived and one of them's ancestral, basically, here in most of these comparisons. So monocots have one cotyledonous leaf. And we'll talk about that more as we talk about germination. And that's a good feature that we find across the group. One embryonic leaf is produced in monocots. Whereas in eudicots, like in other dicots, there are two cotyledonous leaves that we'll look at here again in more detail in a minute. As far, this isn't very helpful, though, because the cotyledons are lost early in development. They're just embryonic leaves that don't persist very long. In terms of identification, it's not a very helpful feature, even though it's consistent. Leafination's a good feature. Monocots have this derived feature of having their veins, the vasculature of their leaves, in a parallel orientation or semi-parallel. As you can see, for example, in a grass leaf. Whereas the veins of a eudicot are often net-like, sort of a reticulum or a web of venation diverging in different angles, which is actually an ancestral feature shared with earlier angiosperms. If you cut open the stem, if you do a cross-section of the stem, and we're gonna get into this a lot more, so I'm just gonna brush over it now. The vascular or conducting tissue in a monocot stem, the vascular tissue in general is in little bundles these little bundles here inside the stems of flowering plants during primary growth. We'll talk more about that later. But it's scattered around inside the stems of monocots, whereas in eudicots, the bundles are arranged in a ring like that, generally speaking. And we'll talk more about that later, but that's something that you can use to distinguish monocots and dicots, eudicots. And as far as roots go, they're very different. And this is important in eudicots, the embryonic root actually continues to develop as a tap root, the main root, and then lateral roots are produced from that. Whereas in monocots, the tap root doesn't persist very long, the embryonic root grows for a while, and then you start getting adventitious roots. And adventitious anything is just something that originates from a point other than its usual origin. So adventitious roots form from the base of stems. So the base of the stem starts producing roots and the tap root doesn't continue to develop. And we end up with a fibrous root system that's often quite shallow like in grasses, a turf root system, whereas in the case of eudicots, you often get a deep tap root. Okay, and we'll have to complete the rest of this next time and we'll get into germination and development right away.