カモメヅル属(ガガイモ科)の花の形態に関する予備的研究

抄録

Result of observation on the floral morphology of 11 species belonging to Cynanchum (Table 1) is given in this paper with preliminary discussion on the taxonomic characters and pollination mechanism of this genus. The result is as follows : Flowers are five-merous with one gynostegium and two carpels. Seplas in bud condition are imbricate in Cynanchum katoi f. albescens, C. japonicum, C. atratum, C. ascyrifolium and C. auriculatum. Corolla lobes in bud condition are imbricate except those of C. ascyrifolium which are not observed, though they have been described as valvate (MURATA, 1981). Several glands are on the adaxial base of sepals in all species. Corona lobes are different in shape according to species, though they are adnate to abaxial face of filaments in all species except C. chinense. In C. japonicum the corona lobes develop ontogenetically from dorsal surface of staminal filaments. Corona lobes are ; small and spheroidal (C. magnificum), ellipsoidal (C. paniculatum, Fig. 2-3), trigonal pyramidal (C. katoi f. albescens, C. ascyrifolium), tongue-shaped and flat part of the corona being tangential to the axis of flower (C. atratum), tongue-shaped with small protuberance on the upper dorsal side of flat part (C. japonicum, Fig. 1 : 1P), tongue-shaped and the upper part of the corona being divided dorsi-ventrally into two finger-like projections and basal part being expanded and folded back to the abaxial surface of corona lobe (C. caudatum, C. officinale, C. auriculatum, Figs. 1 : 2C, 3C), tongue-shaped similar to that of C. caudatum but different from that of C. caudatum in the form of basal part being expanded tangentially and adnate to adjacent corona lobes (C. sibiricum). Corona lobes of C. chinense are tubular in shape and with a couple of hairs dorsi-ven-trally arranged and being outside of five anthers (Fig. 1:4). In all species, each stamen has anther wing which is expanded tangentially. There is longitudinal lacuna between valvately arranged anther wings. Hairs occur from edge of anther wing to the lacuna in all Japanese species. Screen-like small appendage at the apex of each anther is observed in all species. Each anther has two-locules in all species. Twinpollinia which are chinned-type in position are common in all species (Figs. 1:5, 6). Pistil consists of two separate carpels in all species. Placentas are submarginal in all species except C. chinense and C. sibiricum of which plasentas are not observed. The type of placentas is identical with those reported by SAFWAT (1962), though only marginal type has been described in the Asclepiadaceae (CRONQUIST, 1981).