Aestivation - The mode of arrangement sepals or petals in floral bud with respect to the other members of the same
whorl is known as aestivation.
Following are the is known as aestivation.
1) Valvate- when sepals or petals in a whorl just touch one another at the margin, without overlapping
2) Twisted - If one margin of the appendage overlaps that of the next one.
Eg- China rose, ladyfinger, cotton etc.
3) Imbricate - If the margins of sepals or petals overlap one another but not in any particular direction.
Ex- Cassia and gulmohar
4) Vexillary - In pea and bean flower, there are 5 petals, the largest (standard) overlaps the lateral petals (wings)
which in turn overlaps the two smallest interior petals (keel)