Lesson 8 of 13 · 6 min
Calyx, corolla and aestivation
NCERT §5.5.1.1, §5.5.1.2, Figure 5.11
Nithya slices across a fat china rose bud and a pea bud with a razor and looks at the cut ends. In the china rose the petals wind round in one direction like a pinwheel; in the pea the biggest petal wraps around all the others.
The lesson in notes
In short
Calyx: the outermost whorl, made of sepals. Sepals are usually green and leaf-like and protect the flower while it is a bud.
Gamosepalous: sepals united. Polysepalous: sepals free.
Corolla: made of petals, whose bright colours usually serve to draw insects in for pollination. Gamopetalous: petals united. Polypetalous: petals free.
Corolla form varies a great deal. Common shapes: a tube (tubular), a bell, a funnel, or a flat wheel.
Aestivation is the way sepals or petals lie in the bud relative to their neighbours in the same whorl. Main types: valvate, twisted, imbricate, vexillary.
Valvate: neighbouring members just meet at their edges and do not overlap. Example: Calotropis.
Twisted: each member overlaps the next one with one margin, all the way round in one direction. Examples: china rose, lady's finger, cotton.
Imbricate: the margins overlap, but with no single direction. Examples: Cassia, gulmohur.
Vexillary or papilionaceous (pea, bean): five petals; the largest, the standard, overlaps the two lateral wings, and the wings overlap the two smallest anterior petals, the keel.