Abstract: The embryology of Whytockia hekouensis Y.Z.Wang, as a representative of the genus Whytockia, was investigated in order to provide information on the systematics of the genus. The anther wall comprises four layers-epidermis, endothecium, middle layer and tapetum. 2-3-nucleate cells are frequently observed in the tapetum. The anatropous, unitegminal and tenuinucellar ovules, and the embryo sac of the Polygonum type conform to those of the most members of the Gesneriaceae. Twin megaspore mother cells occasionally occur during megasporogenesis. The development of the endosperm is of cellular type. The micropylar haustorium of Whytockia is 2-celled uninucleate in the early development and 2-celled binucleate of 4-celled uninucleate, and sometimes multi-celled in the late development, while the chalazal haustorium is binucleate. The extra - micropylar structure has been observed during the development of the micropylar haustorium. The development of the onagrad type embryo consumes up the endosperm except ont layer that remains in the mature seed. The coat of a mature seed consists of two layers which develop respectively from the outer epidermal cells and the endothelial cells of the integument. The embryology of W.hekouensis is compared and discussed with that of others in the Gesneriaceae.

Key words: Pollen

摘要： 对河口异叶苣苔的胚胎学观察旨在为该属的系统学研究提供参考。该种的花药药壁由表皮、药室内壁、中层和绒毡层4层细胞组成。2～3-核细胞在绒毡层频繁出现。胚珠属倒生,单珠被和薄珠心型。胚囊发育属蓼型。该种胚囊发育中的双大孢子母细胞现象,分别为并列和前后排列型。前者发育至双并列四分体,后者发育到呈棱形的4个大孢子。胚乳的发育属细胞型,并在合点端和珠孔端分别具有吸器。珠孔吸器发育早期为单核、2-细胞，后期为两核、2-细胞或单核、4-细胞，有时为多细胞，并在发育过程中向外伸长形成外珠孔。合点吸器为两核。由于合点吸器和珠孔吸器的活动,位于珠被最外层细胞和珠被绒毡层之间的2～3层细胞逐渐解体和被吸收。胚的发生和发育属柳叶菜型。在胚的发育过程中,胚乳几乎被吸收耗尽,仅剩下一层胚乳细胞紧贴内种皮。成熟种子的种皮由珠被最外层细胞和珠被绒毡层发育而来。本文对河口异叶苣苔的胚胎发育过程同苦苣苔科其它类群进行了广泛的比较和讨论。

关键词: 小孢子, 胚囊, 双大孢子母细胞, 胚, 胚乳, 河口异叶苣苔, 苦苣苔科