 Have you ever noticed how different fruits have seeds arranged in different ways? Ever wonder why? So in order to understand this let's go back and take a look at the process that development of seeds in a fruit in the first place. So we know that a flower has this ovary in its gynecium which has these ovules in it and the ovules house the eggs. So this right here is the ovary and these are the ovules. Now when an ovary matures the ovary turns into a fruit and the ovules they become seeds and the ovules themselves they are arranged inside the ovary in a particular fashion and that arrangement of ovules is called placentation. Placentation is different in different types of plants that's why you see the seeds are arranged in different ways in different types of fruits because the arrangement of the ovules remains the same when the ovules turn into seeds. So why is it called placentation? So let's take a look at the inside of an ovary in more detail. So over here this whole thing is the ovary and these right here are the ovules and you see these structures to which the ovules are attached. So these structures are called the placenta. So the ovules are attached to the ovary via these connecting tissues called the placenta because the ovules are attached to the placenta the way in which the ovules are attached is called placentation. So now let's take a look at the different types of placentation found in different types of plants. In the first type of placentation that we are going to look at the placenta forms sort of like a ridge at one of the margins of the ovary. So this is the ovary and this orange thing is the placenta which forms a ridge and the ovules they are attached to this ridge at the margin. Since the ovules are attached at the margin this type of placentation is called marginal. So it's the same thing that you see in peas this is the pea fruit though this is not the ovary but it's the same type of arrangement of the ovary as well because it's the ovary that turns into the fruit. So this type of placentation as you can see is called the marginal placentation. The next type of placentation kind of looks like a wheel. So in this type of placentation so if this is the ovary the placenta look like this. You see there is the central thing called the axis and then there are these things like the spokes of a wheel and the ovules they are attached to the central axis. Now this you can think of this as the top view of the ovary. If you were to look at it at the ovary from the sides or from the front or the back then the axis the central thing would look like a cylinder and the ovules they are attached to this axis and hence this type of placentation is called axial placentation. Another type of placentation which is similar to axial but you take away the spokes and you get something like this. So here the ovules are still attached to the axis but there are no spokes over here. The ovules are free from the spokes or the septa. Actually these are called septa. These are called septa and the singular form is septum. So in this type of placentation the septa are absent only the axis is there the ovules are attached to the axis but they are kind of free. They are free to be anywhere as long as they're attached to the axis and hence they are called free central. This is free central placentation. In the next type of placentation instead of being attached to something at the center the ovules instead are attached at the periphery at the wall of the ovary. Hence this is called parietal placentation because in Latin parietal refers to something related to a wall. The last type of placentation we are not going to look from the top so all these three types of placentation we were looking at them from the top they were the top view but here we are going to look at the ovary from the sides or from the front kind of like the marginal placentation ovary. So here in this case there is just a single ovule at the base of the ovary the bottom or the base of the ovary and this type of placentation is called the basal placentation. So you've learned about five main types of placentation in this video. Marginal where the ovules are attached at the margin of the ovary. Axial where the ovules are attached at the axis and there are the septal like the spokes of a wheel then there is free central where the ovules are attached at the center and are free to be anywhere they are not bound by the septal walls. Then there is the parietal placentation where the ovules are present at the wall. Parietal means wall so they are present at the wall of the ovary and basal placentation where there is a single ovule present at the base of the ovary.