扁苞蕗蕨和长柄蕗蕨的细胞分类学研究

本文首次报道了四川产扁苞蕗蕨和长柄蕗蕨的染色体及孢子发生情况。它们的染色体数目分别为 n=26和n=28,都是有性生殖的二倍体。染色体基数26在蕗蕨属的发现进一步证明了它和膜蕨属、厚壁蕨属的密切亲缘关系。这两种蕗蕨的孢子囊通常形成128个孢子及少数256个孢子的情况被描述,它们应该被看成是有性生殖真蕨,尤其是在膜蕨科和薄囊真蕨中的其他较原始的类群中的正常的孢子发生路线。

CYTOTAXONOMIC OBSERVATIONS ON MECODIUM PANICULIFLORUM(PRESL)COPEL.AND M.OSMUNDOIDES(V.D.B.)CHING

Mecodium paniculiflorum(Presl)Copel.and M.osmundoides(v.d.B.)Ching from Sich- uan Province have been examined cytologically.They have the chromosome numbers n=26 and n=28 respectively,which are recorded for the first time.Their spores produced after normal meiosis are seemly available.Both the species are sexual diploid.The chromosome numbel n=26 of M.paniculiflorum shows that it is distinct from M.polyanthos(Sw.)Copel.with the chromosome number n=28.However,M.osmundoides has the same chromosome number with M.polyanthos.Therefore,it may be an Asian member of M.polyanthos group. The occurrence of the basic number 26 in the genus Mecodium has given a strong evidence of the close relationship between Mecodium and Hymenophyllum,Meringium.It has been known that in Hymenophyllaceae,they are the only three genera with more than four base numbers.They have shared the base numbers 21 and 28.Now,they have the third common base number 26(or 13)which is a spicific basic number in the family.In addition,all they have bivalved involucres and other similar characters,so it is reasonable that they are treated as subgenera or section under the same genus Hymenophyllum by C.V.Morton and K.lwa- tsuki. During the sporogenesis of M.paniculiflorum and M.osmundoides,the initial archesporiat cell in a developing sporangium usually divides successively five times by mitosis resulting 32-spore mother cells,and then meiosis occurs regularly,giving rise to I28 spores finally.In a few cases,64-SMC or 256-spore sporangia are also produced in M.osmundoides.It is suggested that besides forming 64-spore sporangium,forming 128-spore and 256-spore sporangia should be conscidered as normal sporogenesis lines in sexually-reproducing ferns,especially in Hyme- nophyllaceae and other ancient group of leptosporangiate ferns.The voucher specimens are deposited in the Herbarium of our Institute(PE).