This aestivation is imbricate.
The circular aestivation is generally associated with a regular calyx and corolla, while the spiral aestivations are connected with irregular as well as with regular forms.
When the parts of a single whorl are placed in a circle, each of them exhibiting a torsion of its axis, so that by one of its sides it overlaps its neighbour, whilst its side is overlapped in like manner by that standing next to it, the aestivation is twisted or contorted (fig.
This variety of imbricate aestivation has been termed cochlear.
The manner in which the parts are arranged in the flower-bud with respect to each other before opening is the aestivation or praefloration.
When the parts of a whorl are placed in an exact circle, and are applied to each other by their edges only, without overlapping or being folded, thus resembling the valves of a seed-vessel, the aestivation is valvate (fig.
When the parts of a whorl are five, as occurs in many dicotyledons, and the imbrication is such that there are two parts external, two internal, and a fifth which partially covers one of the internal parts by its margin, and is in its turn partially covered by one of the external parts, the aestivation is quincuncial (fig.
Those forms of aestivation are such as occur in cyclic flowers, and they are included under circular aestivation.
Giving rise to vexillary The order of the cycle is indicated aestivation (fig.
The edges of each of the parts may be turned either inwards or outwards; in the former case the aestivation is induplicate (fig.