Floral parts of leaves on thalamus-digieduco

Insertion of Floral Parts Of Leaves on Thalamus :  Hypogyny, perigyny and epigyny are the terms applied to the different floral parts of leaves constructions which indicate the structure of thalamus(i.e. the floral axis) and the consequent. position and insertion of calyx, corolla and androecium in relation to the pistil.

A. IN HYPOGYNOUS flower, which are very common in dicotyledonous as well as in monocotyledonous plants (e.g. in families Ranunculaceae, Cruciferae, Solanaceae, Convolvulaceae etc.) the thalamus is short, either convex or conical or fairly long (as in Michelia champaca, species of Ranunculus, Gynandropsis, etc.) with either whorled as well as spiral arrangement of floral leaves or both whorled and spiral arrangements of floral leaves (i.e.spirocy clic) ; the pistil or gynoecium is at the top most position; stamens, petals and sepals are all inserted successively on the thalamus below the pistil. In this case the position of the ovary is superior

B. IN PERIGYNOUS flowers , the thalamus is flat or concave. When the thalamus is flat, the pistil is located in the centre surrounded by stamens, petals and sepals successively e.g. Pisum sativum, Crotalaria juncea (Papilionaceae) etc. When the thalamus is cup-shaped or concave, the sepals at the base are united forming a calyx tube which is adnate to the concave thalamus. The calyx lobes, the petals and stamens are, inserted at the rim of the thalamus cup surrounding the pistil in the centre. In the perigynous condition, the ovary of the pistil is free from lateral adnation of the cup shaped thalamus inside ;so in perigynous flower there is no adnation of ovary-wall with the thalamus except at the base. Such perigynous flowers are found in most Rosaceae, in some Lythraceae e.g. lagerstroemia sp. etc. In this case the ovary is either superior or half-inferior in position.

C. IN EPIGYNOUS flowers, found in the members of the families Myrtaceae, Compositae, Rubiaceae etc., the thalamus forms a deep concave cup to which the calyx tube is adnate. The ovary of the gynoecium finally becomes completely fused with the receptacular wall (receptacle means deep adnate and concave thalamus) inside-as a result the calyx lobes, petals and stamens are put and inserted above the ovary of the gynoecium. In this case ovary is inferior in position in relation to petals and stamens. Epigyny is more advanced structure in phylogenetic evolution, it is ultimately derived from perigyny in course of evolution.