Abstract:

Ginkgo biloba var.epiphylla,with important ornamental and scientific values,is an extremely peculiar germplasm.It is reported that the number of G.biloba var.epiphylla is only 47 in the whole world,their age ranged from 36 to 1200.As far the whole tree is concerned,the epiphyllous ovules(seeds)accounted for 5% to 25% of the total ovules(seeds)produced by the tree.The paper reviews many opinions about the taxonomic status,summarizes the distribution,and the previous study on G.biloba var.epiphylla,comprising the morphology,anatomy,cell biology,molecular biology.The morphogenesis of Ginkgo female reproductive organ from the teratological data of G.biloba var.epiphylla,possible relationships and possible genesis mechanism of G.biloba var.epiphylla are discussed in the paper.The whole reproductive short shoot of G.biloba correspond to the a megasporophyll strobilus(female cone).G.biloba var.epiphylla may have a close relationship with the Pteridospermidae and Cycas.There are atavism theory,senile form theory and environment inducement theory with respect to the genesis mechanism of G.biloba var.epiphylla.After all-round analysis,we think they may be a chimera,and their occurrence may relate to the expression of homeobox gene.The main problem existed in the study of G.biloba var.epiphylla is presented.

Key words: Ginkgo biloba var.epiphylla, morphogenesis, ontogeny, phylogeny, genesis mechanism