小蓬草的胚胎学研究

对小蓬草（Conyzacanadensis）大小孢子发生、雌雄配子体形成、受精、胚及胚乳发育过程进行了研究，主要结果如下：花药四室，药壁由表皮、药室内壁、中层和绒毡层组成。表皮退化；药室内壁宿存，细胞柱状伸长，纤维状加厚；中层细胞退化较早，在小孢子母细胞减数分裂开始时仅存残迹；绒毡层于小孢子母细胞减数第一次分裂前期开始原位变形退化，属于腺质型绒毡层；小孢子母细胞减数分裂为同时型，四分体的排列方式主要为四面体形和左右对称形；成熟花粉粒多为3-细胞花粉粒，偶见2-细胞花粉粒。子房下位，2心皮，1室，单胚珠，基生胎座；单珠被，薄珠心，倒生胚珠，具发达的珠被绒毡层。珠心表皮下分化出大孢子孢原细胞，孢原细胞直接发育为大孢子母细胞，大孢子母细胞减数分裂形成4个大孢子直线形排列，仅合点端的大孢子发育成功能大孢子母细胞，胚囊发育为蓼型。两个极核在受精前融合为次生核，珠孔受精。胚乳发育属于核型，胚胎发育为紫菀型；具胚乳吸器。

Studies on Embryology of Conyza canadensis (L.) Cronq

The microsporogenesis, megasporogenesis, the development of male gametophyte, female gametophyte, embryo and endosperm, and double fertilization of Conyza canadensis （ L. ） Cronq were studied in this paper. The results show as follows：the anther is tetrasporangiate and its mature wall comprises of an epidermis,endothelium,a middle layer and a single-layered tapetum;the epidermis degenerates;cells of endothelium persisted arc columnar and with fibrous thick walls;the middle layer degenerates early and only a vestige can be observed at meiosis-I of microsporocyte ; the tapetum belongs to glandular type, generally,is out of shape and degenerates early at meiosis-I of microporocyte;cytokinesis in the microsporocyte meiosis is of the simultaneous type, and the microspore tetrads are tetrahedral or isobilateral;pollen grains are mainly 3-celled, and occasionally 2-celled ;the ovary is bicarpellate, unilocular, one ovules and basal placenta ; the ovule is unitegmic, tenuinucellate, anatropous and with developed endothelium ; arches- porial cell of megaspore differentiates immediately below the nueellar epidermis and functions as megasporocyte after development, and then, the megasporocyte undergoes meitotic to form a linear tetrad, only one chalazal megaspore in linear tetrad becomes the functional megaspore ; the embryo sac is of the Polygonum Type;two polar nuclei melt into a secondary nuclei before fertilization;fertilization is porogamous;the development type of the endosperm is Nuclear Type, and the embryogeny belongs to the Asterad Type ; endosperm haustorium is present.