ミヤマニガウリ(ウリ科)の花部形態 Floral Morphology and Vasculature of Schizopepon bryoniaefolius (Cucurbitaceae)

雄性両全性異株の蔓性一年草であるミヤマニガウリ(ウリ科カボチャ亜科ミヤマニガウリ連)の花の特徴,とくに雄しべ・子房室の配列,維管束走行,蜜腺,毛,フェノロジーを観察した。両性花・雄花とも2個の2葯性雄しべと1個の1葯性雄しべを持つ。このような雄しべ構成はウリ科カボチャ亜科の多数の分類群に見られるが,それらでは2葯性雄しべに2本の維管束が入るのに対して,ミヤマニガウリでは各雄しべに入る維管束は1本で,むしろ2葯性雄しべを3本持つグループ(スズメウリなど)と共通する。他のウリ科の多くと同様に葯と葯隔の境界付近に大きな基部細胞を持つ毛があるが,その形状は他の属で既知のものと異なり,球形の細胞が積み重なっている。両性花では葯の裂開と柱頭の成熟のあいだの時間差が小さく,雌性期と雄性期は大きく重なっている。両性花・雄花ともカップ状の花托の底部に蜜腺がある。

Floral characters of an annual androdioecious vine Schizopepon bryoniaefolius (Cucurbitaceae-Cucurbitoideae-Schizopeponeae) are described with special reference to the arrangement of stamens and ovary locules, vasculature, nectaries, trichomes and phenology. Both hermaphrodite and male flowers bear two dithecal and one monothecal stamens, as in many taxa of Cucurbitoideae. However, S. bryoniaefolius differs from them in that each stamen is recognized as a single mound in an early stage of the development and receives a single vascular bundle. The anther trichomes are snowman-like and are different in cell shape from those of the other previously examined taxa. There is no or small time-lag between anther dehiscence and stigma maturation in hermaphrodite flowers. In both of the sexual morphs, there is a nectary at the bottom of the receptacular cup.