枫杨中两性花的发现

Discovery of Bisexual Flowers in Pterocarya Stenoptera C. DC.

This paper reports the bisexual structure of the flowers of Pterocaryastenoptera. The bisexual flowers are borne at the end of a leafy shoot of the current yearin many-flowered terminal pendulous catkins. They have the same structure as the generalfemale ones. Each flower grows in the axil of a bract,  with a pair of bracteoles and foursmall perianths. Each flower has two or three carpels in the centre of the flower,  and uponthem there are two or three styles with stigmas on the inner face. They differ from the ge-neral female ones in that each of them contains 4-6 stamens,  forming a single whorl. Thestamens alternates with,  or is opposite to,  the perianth elements. Sometimes they contain8 (-10) stamens,  forming two whorls,  with 6 in the outer whorl and 2 (-4) in the in-ner whorl, and in this case the pistil in the bisexual flower of terminal catkins often becomesa rudiment.      It is interesting that we have also found bisexual flowers in another tree,  which areborne in lateral male catkins. They have the same structure as general male ones,  and thepistils are often represented by a rudiment.      Manning (1940) points out that some female flowers of Pterocarya stenoptera and P.fraxinifolia occasionally have stamens ( ? ) opposite the sepals. In P. stenoptera we have foundthat both the stamens and the stigmas of bisexual flowers are functional. They are capableof producing functional fruits. This is the same case as in Myrica Gale described by Daveyand Gibson (1917). Rendle (1952) points out that in the male flowers of Platycarya thepistils often appeared as a rudiment. He considers,  however,  the male flowers derived fromthe bisexual flowers with an indefinite number of stamens. The rudimentary pistils of later-al male catkins in P. stenoptera we found are just the same as the ones found in Platycaryaby Rendle.      The discovery of the bisexual flowers in P. stenoptera may prove that the unisexualflowers of the present-day Juglandaceae are derived from ancestors with bisexual flowers.This tends to support the hypothesis that Cycadicae is the possible ancestor of the angiosperms.