MORPHOLOGICAL DIFFERENCES AND CHANGES OF THE GYNOECIUM IN SHORT-LIVEDFLOWERS OF ROSA-SETIGERA MICHAUX AND THEIR RELATIONSHIP TO DIOECY

Rosa setigera is unique within the genus because the plant is cryptica lly dioecious, the Rowers of male and female plants appearing identica l. Flowers produce no nectar, and the plants rely upon insects, which feed on or collect pollen, for pollination. The plants' gynoecia in bo th sexes are extremely similar; however, overall the synstigmatic leng th, synstylar length, ovary length, ovule length, and ovule width are greater in flowers of female plants than in flowers of male plants. On ly the single stigma width of male plants was found to be greater than that of female plants. Furthermore, ovary volume, ovary width, ovule length, ovule width, and ovule volume in flowers of female plants incr ease over the period of 4 d of a flower's life (i.e., with petals), wh ereas in flowers of male plants those characters either decrease or re main relatively constant over the 4-d time period. No overall differen ces in synstigmatic width, synstylar width, single stigma length, syns tigmatic area, and ovary width were found. The results indicate that d ioecy may be a relatively recent occurrence in this species.