A contribution to the floral morphology and embryology of Dendrophthoe falcata (L. f.) Ettingsh.

Abstract

SUMMARY 1 The flower is pentamerous. There is a five-toothed calyculus and a perianth tube, which opens at the tip into five reflexed lobes and bears five epiphyllous stamens. The ovary is inferior. 2 The floral organs arise in acropetal succession. 3 The vascular anatomy of the flower is based on a pentamerous plan. The perianth tube receives five vascular traces each of which divides to form three to five bundles. The stamens receive one trace each, and five traces enter the style. In the stigmatic region they further subdivide into seven to ten bundles. 4 The anther wall is formed of four layers besides the epidermis. These are the endothecium, two middle layers, and the tapetum. The tapetum remains uninucleate. 5 The microspore mother cells divide simultaneously to form microspore tetrads of tetrahedral and decussate types. 6 The pollen grains are shed at the two-celled stage. The division of the generative cell, which takes place in the pollen tube, shows clear spindle fibres accompanied by cell-plate formation. 7 The archesporial tissue differentiates in the hypodermal layer at the bottom of the ovary cavity. 8 The megaspore mother cells give rise to linear tetrads of megaspores. All the megaspores except those lying towards the upper end are capable of further development. As a result of the enlargement and gliding growth of the megaspores the ovary cavity is soon obliterated. 9 The embryo sac is eight-nucleate. The upper ends of the embryo sacs grow into the wall of the style, while the lower ends grow downwards so as to reach the pad of collenchymatous cells situated in the basal part of the ovary. A well-developed embryo sac is approximately 22–28 mm. in length. 10 The first division of the egg is longitudinal. Owing to an extreme elongation of the suspensor the pro-embryos are pushed down into the ovary. Only one embryo reaches maturity. 11 The endosperm is cellular and is initiated in the lower part of the embryo sac. Due to a dissolution of the separating walls of the embryo sacs all the endosperms fuse to form a composite mass. 12 There is no testa. The wall of the fruit comprises four layers of tissues. Of these the second (counting from outside), or the viscid layer, is very characteristic and is responsible for the ejection of the seed and its adhesion.