Define ptyxis.

Explanation

Rolling or folding of individual leaves is called ptyxis. There are seven types of ptyxis as follows :
1. Reclinate - When the upper half of the leaf blade is bent upon the lower half as in loquat (Eriobotrya japonica).
2. Conduplicate - When the leaf is folded lengthwise along the mid-rib, as in guava, sweet potato and camel's foot tree (Bauhinia).
3. Plicate or Plaited - When the leaf is repeatedly folded longitudinally along ribs in a zig-zag manner, as in Borassus flabellifer.
4. Circinate - When the leaf is rolled from the apex towards the base like the tail of a dog, as in ferns.
5. Convolute- When the leaf is rolled from one margin to the other, as in banana, aroids and Indian pennywort. Musa und members of Araceae.
6. Involute - When the two margins are rolled on the upper surface of the leaf towards the mid-rib or the centre of the leaf, as in water lily, lotus, Sandwich Island Climber (Antigonon) and Plumbago.
7. Crumpled - When the leaf is irregularly folded as in cabbage.