ONTOGENY OF STAMINATE AND CARPELLATE FLOWERS OF SCHISANDRA-GLABRA (SCHISANDRA)

Schisandra glabra (Schisandraceae) is a rare monoecious liana in fores ts of the southeastern United States, Both types of flowers are solita ry in leaf axils and radially symmetrical, with eight to 13 greenish y ellow to red tepals in the flower. Each male flower has five (four to seven) spirally arranged stamens forming a red pentagonal synandrous s hield. Transitions between tepals and stamens occur occasionally. Each carpellate flower contains 25-30 free, spirally arranged carpels on a conical receptacle. Histological study shows that the floral apical m eristem is more highly convex than the vegetative apex; both have tuni ca-corpus configurations. All primordia, starting with tepals, are ini tiated acropetally, in a continuous 2/5 phyllotaxis. Apical diameter i ncreases greatly after tepal initiation, more so in carpellate than in staminate flowers. The apical residuum in staminate flowers expands t o form the center of the staminal shield, with the stamen primordia pr ojecting as flattened marginal extensions. The connective region of ea ch stamen broadens markedly, resulting in wide separation of the spora ngial pairs of each stamen. Just before anthesis, each connective arch es outward so that the sporangia appear lateral. In carpellate flowers , the carpel primordia are initiated helically, the apical residuum fo rms a narrow, spinelike structure. Floral development in Schisandra a is compared with that of other primitive angiosperms such as Illicium and Myristica.