Floral Morphology and Embryology of Samadera indica

Abstract

1. The morphology and vascular anatomy of the inflorescence shows that the so-called umbel of Samadera indica is a condensed thyrsoid inflorescence. 2. The flowers of S. indica and S. lucida are pedicellate, bracteate, actinomorphic, dichlamydous, bisexual, hypogynous, and tetramerous. The vascular anatomy of the two species is similar. Each sepal has a gland on the dorsal side. The sepal laterals arise commissurally. The petal is a single-trace organ. 3. The stamens are in two whorls of four each. Anatomically there is no indication of obdiplostemony. Each stamen has a bilobed scale at the base of the filament which is interpreted to be stipular in nature. A single trace enters the filament of each stamen and becomes siphonostelic. The filament is considered to correspond to a petiole. 4. The vascular supply to the disk occurs on radii alternating with the carpellary supply. The disk breaks up into four lobes, each lobe alternating with the antepetalous free carpels. The disk is considered to be a modified outer whorl of carpels. The residual vascular tissue that remains above the level of the ventral traces, after giving rise to branches that fuse with the ventral bundles, continues to the prolongation of the floral axis. The floral parts are considered to be lateral organs, and the bundles fusing with the ventrals are interpreted as belonging to a third whorl of carpels. 5. The anther wall consists of epidermis, a fibrous endothecium, multinucleate secretory tapetum, and two to three middle layers. The pollen grains are shed at the two-celled stage. 6. Ovules are bitegmic, crassinucellate, and anatropous. The inner integument forms the micropyle. A well-developed hypostase is connected to the chalazal end of the embryo sac by a few rows of elongated cells. The funicular vascular strand terminates beneath the chalaza. The nucellar cells are multinucleate. The nucellar epidermis divides to form a cap. 7. The hypodermal ovular archesporium consists of three to four cells, of which only one generally develops further. The tetrad is linear; the chalazal spore develops into a Polygonum type of embryo sac. The mature embryo sac has lateral haustoria in the chalazal end. Antipodals are ephemeral. Twin and multiple embryo sacs and a case of reversed polarity have been observed. 8. Fertilization is porogamous. Double fertilization and triple fusion have been observed. The endosperm is free nuclear.