The arrangement of accessory whorls (calyx, corolla) in relation to one another in the floral bud is called as aestivation.
The different types of aestivation are:
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Type
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Description
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Arrangement
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1. Valvate
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Petals or sepals meet each other at the edges.
Arranged without overlapping
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Calyx of Hibiscus
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2. Twisted
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Petals or sepals show overlapping.
Overlapping is done by one margin of each petal over the margin of adjacent petals
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Corolla of Hibiscus
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3. Imbricate
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Margins of petals overlap each other in such a way that one petal is completely external, one petal is completely internal
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Cassia, Bauhina
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4. Vexillary
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It is seen in papilionaceous form of corolla.
Posterior petal is external and largest, it almost covers the two lateral petals and lateral petals in turn overlap two smallest anterior petals
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Pisum sativum (Garden Pea)
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5. Quincuncial
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Margins of petals overlap each other in such a way that two petals are completely external, two petals are completely internal
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Psidium guajava
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