Abstract:

This paper studied on the floral syndrome of Cynanchum otophyllum, visiting insects and their foraging behavior. The results showed that the floral morphologies were complex . Two separate ovaries were united by their styles to form a gynostegium with anthers . The stigmatic surfaces were enclosed by the tightly abutting wings of adjacent anthers to produce five stigmatic chambers . C. otophyllum possessed pollinia , which permited the transfer of hundreds of pollen grains at a time . Honeybees ( Apis cerana Fabricius) were primary pollinators . The process of C. otophyllum pollination was : ( 1) removal of a pollinarium: when the groove in the corpusculum catched on mouthparts or legs of honeybees and was forcibly pulled from the flower, and (2) insertion of a pollinium: when a pollinium lodged in a stigmatic chamber . Following successful
insertion , the pollens germinated within the stigmatic chamber and pollen tubes subsequently grew down the stylar
canal and finally entered the ovaries . The durable covering of pollinia allowed a long residence time on pollen viability , so
the pollen could remain a relatively high viability in the flower period . Stigma receptivity , however , decreased gradually
over the seven-day life span of flowers .

Key words: Cynanchum otophyllum