 Flowers are not only beautiful, they actually have an amazing variety. If you look at the colors, their shapes of petals, the variety is staggering. It's also the arrangement of the petals, the sepals and other parts of the flower which varies from flowering plant to flowering plant. And in this video we are going to look particularly at the different arrangements of sepals and petals. Take a look at the sepals of this flower. See how they are all joined together at the base. So whenever the sepals are joined together, they are called gamma sepals. Gamma means marriage. So just as in a marriage two people are together, similarly in gamma sepals calyx, this is a calyx, as you know the calyx consists of all the sepals of a flower. In a gamma sepals calyx, the sepals are all together. The opposite of gamma sepals is polysepals in which, like in rows, as you can see the sepals are completely separate. They are not joined together at all. So the term for that is polysepals. Poly as you know is many and there are many sepals which are separate. That's why we call them polysepals. And we have a very similar thing going on for petals as well. So for example in this flower, as you can see the petals are all kind of joined together. Hence what do you think we'll call them? Gamma, petalus. And just like polysepals, we have something called polypetalus. Like in the hibiscus flower, all the petals are completely separate from each other. So this is called polypetalus. Corolla. As you know, corolla consists of the petals. So polysepals calyx, polypetalus corolla and here it's gamma petalus corolla. Now we are going to look at how petals and sepals are arranged with respect to each other in a flower and the term for that is estivation. So estivation is nothing but arrangement of sepals or petals. So take a look at this hibiscus flower. I want you to concentrate on the sepals. So if you look at the sepals, they are just side by side one after another, right? So if you look from the top, this is what it looks like. This is the arrangement of the sepals of the hibiscus flower. So each of these represent a sepal and they are side by side. This is the simplest arrangement of sepals or petals and this type of arrangement is called valvate. So this is valvate estivation. So keep in mind that whatever estivation I talk about, it's applicable to both sepals and petals. So valvate estivation can belong to sepals as in this case. It can also belong to petals which is not so in this case. If you look at the petals of a hibiscus flower, you will see a different picture than from the sepals. They are not exactly side by side. There are overlaps at the edges. For example, this edge of this petal is on top of the edge of this petal whereas the other edge of the same petal is below the edge of the next petal. So if you look at it anti-clockwise, it's in the same direction of overlap. What do I mean by this? For example, let's start with this petal. Its left edge is over the edge of the previous petal and its right edge is below the edge of the next petal. Similarly for this petal, its left edge is over the edge of the previous petal. Whereas its right edge is under the edge of the next petal. And the pattern follows. It's the same for all the petals. So if you look at the estivation, it looks like the valvate estivation has been taken and have been kind of twisted. So that's why this kind of estivation is called twisted estivation. Another type of estivation is a little more complicated. For example, if you look at this flower, you see this particular petal. For both edges it is under the adjacent petals. Whereas for these two petals, the story is a little bit different. For both of these petals, one of the edges are above the adjacent petal and the other of the edges are below the adjacent petal. So this is more complicated than both valvate and twisted. And the name for this is imbricate. So the same pattern as the petals, so this petal overlaps both of the adjacent petals. Whereas the adjacent petals in turn overlap a little bit differently. So in imbricate estivation, so this is called imbricate estivation. See this petal, both the edges are over the edges of the adjacent petals. Whereas for each of these adjacent petals, one of the edges are over the adjacent petal, whereas the other edges below the adjacent petal. And the same goes for this petal, whereas this petal is the opposite of this one. Both of its edges are under the edges of the adjacent petal. So it's kind of complicated and it's called imbricate. The way I remember this word imbricate is it sounds kind of like intricate to me. Intricate means complicated. So this is imbricate estivation. The last kind of estivation that we are going to look at is found in the pea flower and all the flowers that belong to the pea family. In this estivation, it looks very different from all the other estivations. There is a big petal which overlaps all the other petals and then there are these two petals which are overlapped by the biggest petal and then there are the smallest petals which are overlapped by all the other petals. So let's look at the diagram, simplified diagram. So this is the biggest petal that overlaps all the others and it's called the standard. A standard means a flag or a banner and this is kind of big, kind of like a flag or a banner. Hence it's called the standard. The standard overlaps these two petals which are present on the sides and are called wings and then the innermost petals which are overlapped by everything else are the smallest ones and kind of present at the base of the petal. They are called keels. Keel is the name given to the structure, the base of a ship that gives support. Since this is also present at the base of the flower, it's called the keel and I'm calling these two petals and yet there is this link between these two. That's because often in this type of estivation the keel petals are joined at their bases and this type of estivation is called the vexillary estivation present in the pea family. So we have looked at how sepals and petals can be attached or free and are called camo sepals, camo petalous, polysepals or polypetalous and what estivation is and the different types of estivation, valveate, twisted, imbricate and vexillary.