Abstract: The work of cytological investigation on Chinese ferns has just begun. The present paper deals with the cytological observation on some Chinese ferns. The materials examined were collected from Emei Shan (Mt. Omei), Sichuan province and Wuling Shah, Xiang Shah, Beijing. Most materials were fixed in field, but the materials for three species were from introduced plants grown in the garden of Botanical Institute. The young fertile fronds were fixed in 1:3 acetic acid-alcohol for 24—48 hours, then they were transfered into 95% alcohol, at last into 70% alcohol. After having been brought to the laboratory, they were stored in the refrigeratory. The spore mother cells (SMCs) of the materials were examined byaceto-carmine squash method in one to two months. The chromosome counts of 12 species of ferns are summarized in table 1. Among them the chromosome numbers of nine species, namely, Adiantum edentulum n = 30, Athyriopsis erecta n = 40, Athyrium fallaciosum n = 40 (and "n" = 80?), Dryopteris julaodongensis "n" = 82 (and n = 41?), Dryopteris sparsa var. nitidula n = 41, Glaphyropteridopsis rufostraminea n = 36, Lunathyrium vegetius n = 80, Polystichum hecatopteron n = 41 and Pronephrium penangiana n = 36, are recorded for the first time. Our observation of the chromosome numbers of Mattcuccia struthiopteris has proved that the base number for this genus is 39. Cytologically, Dryopteris julaodongensis and Athyrium fallaciosum are quite inter. esting. In D. julaodongensis, both 8-SMC and 16-SMC and both 32-spore and 64-spore spo- rangia respectively were observed in the same individual plant, which suggests that it may be a facultative (Dopp-Manton type apomictic and normal sexual) diploid species. So far we have failed to find the clear image of the SMC with 41 bivalents, but n = 41 should be infered. In A. fallaciosum, 40 bivalents formed by relatively completely paired chromosomes can be seen at diakinesis in SMCs, but the Latter course of meiosis, from metaphase Ⅰ to forming young spores, is highly irregular. A number of lagging chro- mosomes and a few of chromatid bridges are present at anaphase Ⅰ and Ⅱ, and more or less micronuclei of unequal size can be observed at telophase Ⅱ or Young spores. A few SMCs at telophase or young spores contain only micronuclei of unequal size without the main nucleus, or otherwise a few of another young spores contain two large nuclei which result in the unequal trispore instead of the normal equal tetraspore. Finally, in a few sporangia, each sporangium gives 64 nearly regular spores, but in the better part of the sporangia, there are less than 64 spores highly irregular in size and shape. Besides in a few other sporangia of the same individual plant, there are 32 nearly regular spores. The above information shows that this plant should be diploid, but the highly irregular course of meiosis in its SMCs is very similar to that in the hybrid. After examining many herbarium specimens we saw that producing irregular aberrant spores in this species is not an accidental, but a common phenomenon (e.g. in material from Kansu province, see plate. Ⅱ fig. 16). It seems that this species is a facultative (both sexual and apomictic). We wonder if it is actually segmental alloploid. Are those irregular phenomena resulted from the precocious desynapsis and segregation of some paired chromosomes, or from the delayed anaphase? And what is the actual breeding system of it ? These problems await futher investigation. The voucher specimens of all species recorded here are preserved in the Fern Herbarium of our Institute. We are indebted to Prof. R. C. Ching for idefitification of the materials used in the present study.