星叶草的形态学研究(1)——胚胎发育过程

本研究的目的在于揭示单型属——星叶草属有关种系发生的胚胎发育性状。胚胎学     研究表明，在分析该属性状演化时下列特征是十分重要的：星叶草具有横生的、单珠被、薄     珠心胚珠; 胚囊形成为蓼型; 初生胚乳核首次纵向分裂形成两个细胞，胚乳发育为细胞型; 胚胎     发育类型基本上属于石竹型; 在胚胎发育的早期阶段，珠被萎缩并且最后消失，因此在成熟果     实中不形成种皮。根据胚胎学和一些形态学证据，作者认为星叶草属同毛茛科及其近缘科之间似乎没有密切的关系。星叶草属的亲缘关系仍有待于进一步研究。

Morphological Studies on Circaeaster agrestis Maxim. (1) Process of Embryolo gical Development

The present paper aims at discovering the characters of embryological development of Circaeaster agrestis, which makes up a monotypic genus, Circaeaster, to establish the phylo- genetic relationships of the genus.  The different opinions on its systematic position among bo- tanists are briefly explained.       The embryological studies show that the most important advanced characters of the genus are as follows.  The ovule is amphitropous, unitegmic and tenuinucelar; the embryo sac forma- tion is in accordance with the Polygonum type; endosperm formation is of the cellular type, the primary endosperm nucleus dividing to form two cells and the first wall vertical; embryo formation follows the variation of the Caryophyllad type; at the early stage of development of embryo, the integument has been already atrophied and at last disappeared, so that the seed coat is absent in the mature fruit.        On the basis of the embryological and some morphological evidence, the authors consider that a close relationship between the genus and Ranunculaceae and its related families seems to be unlikely.  The affinities of the genus Circaeaster are still uncertain.