Spermatogenesis and Oogenesis in Ephedra trifurca

作者：W. J. G. Land · 发表于：Botanical Gazette · 年份：1904 · DOI：10.1086/328518 · 被引用次数：40 · 研究领域：Plant Reproductive Biology、Plant Molecular Biology Research、Plant Pathogens and Fungal Diseases

Ephedra trifurca is monosporangiate, but bisporangiate strobili occasionally occur. The beginnings of the staminate flower were clearly apparent in December, and the pollen was shed about the middle of April, the interval being thus a little over four months. The anthers develop in acropetal succession on a strobilus, and are surrounded by a perianth. Microspore mother-cells were observed about the middle of February, and the reduction division occurs about one month later. The gametophyte number of chromosomes is twelve. There are two persistent prothallial cells; the first is cut off by a wall; the second is not cut off by a wall. The primary spermatogenous cell surrounds itself by a membrane (Hautschicht?), and on the division of the primary spermatogenous cell, the stalk cell and body cell continue to be surrounded by this membrane, and are not separated from each other by a wall. The only wall formed in the pollen grain is the one which cuts off the first prothallial cell. The male gametophyte at the time of shedding consists of two prothallial cells, stalk cell, body cell, and tube nucleus. The megasporangium is surrounded by two integuments, the outer of which consists of four fused leaves; the inner of two fused leaves. The megaspore mother-cell is deeply placed within the nucellus and gives rise to either three or four megaspores arranged in a row, the most deeply placed megaspore being functional. The nuclei resulting from the division of the megaspore show polarity...