Morphology and Embryology of Sebastiania chamaelea

Abstract

1. The embryonic, adult, inflorescence, and floral apices show a two-layered tunica. The marginal growth of the leaf is of the submarginal type and middle subtype. The pattern of growth of cotyledon, bract, perianth, stamen, and carpel follows that of the foliar organs. 2. There is variation in the structure of the cotyledonary, foliar, bracteal, and floral nodes. This is interpreted to indicate the evolutionary course taken by the different nodes in the same individual. 3. The bract, tepal, and stamen receive one trace each. The gynoecium shows three dorsal bundles, three septal bundles, and three placental bundles. The latter constitute the supply to the ovules. 4. The meristematic regions which give rise to the sporogenous cells are confined to the sides of the stamen primordium. Sporogenous cells arise from derivatives of the second tunica layer. 5. There are two to three rows of archesporial cells in the anther lobe. The wall of the anther consists of epidermis, fibrous endothecium, two middle layers, and a secretory multinucleate tapetum. Meiosis in the microsporangium is simultaneous. Pollen grains are tricolporate and shed at the two-cell stage. 6. A nucellar beak and hypostase are present in the bitegmic, anatropous ovule, and a well-developed obturator penetrates the micropyle. The chalazal spore of a linear or a T-tetrad develops into the eight-nucleate embryo sac (Polygonum-type development). 7. The endosperm is free nuclear initially but ultimately becomes cellular. Embryo development is of the Onagrad type. The apical organization of the embryonic root corresponds closely to type I of Haberlandt. 8. The seed coat is derived from both integuments. A caruncle develops from the outer integument.