长喙毛茛泽泻的胚胎发生

对长喙毛茛泽泻（Ｒａｎａｌｉｓｍａｒｏｓｔｒａｔｕｍ）胚及胚乳的发育进行了研究．合子横向分裂成基细胞和顶细胞，基细胞不再分裂，顶细胞分裂形成胚体及合点端胚柄细胞．胚发育属石竹型．成熟胚为“Ｕ”形．胚乳发育属沼生目型，初生胚乳核在近合点端横向分裂，形成两个不等室，即合点室和珠孔室．合点室细胞不再分裂，珠孔室细胞经游离核分裂后，从珠孔端及合点端同时开始细胞化．细胞化与成膜体、细胞板有关，而不是通过“自由生长壁”．随着胚的发育，胚乳逐渐解体，成熟种子中无胚乳．在原胚发育时期，胚柄基细胞及合点室胚乳细胞体积增大，核染色深，有时分裂成２～３核，细胞质浓厚．它们在四形胚时期开始退化，与胚乳细胞化相对应，推测它们与胚早期发育所需营养的供应有关．

EMBRYOGENESIS IN RANALISMA ROSTRATUM

The embryo and endosperm development in Ranalisma rostratum was studiedin this paper. The zygote divides by a transverse wall to form hasal and apical cells. The larger hasal cell undergoes no further division and becomes the hasal suspensor cell,while thesmall apical cell develops into the embryo proper and chalazal suspensor cells. The embryodevelopment conforms to the Caryophyllad type. In the mature seed .the embryo is U--shapedand forms the embryonic shoot apex accompanied by one intraseminal leaf. The endospermdevelopment belongs to the Helobial type. The primary endosperm nucleus (invariably lyingin the chalazaol part of the embryo sac) divides and forms a large micropylar and a small chalazal chambers. The chalazal endosperm chamber remains uninucleate,and free nuclear divisions occur in the micropylar chamber. Cellularization of the endosperm begins simultaneously from the micropylar and the chalazal ends. The cellularization is related to phragmoplastand cell plate .and does not arise from the free growth wall. Accompanying the embryo development,the endosperm degrades and does not exist in the mature seed. In the proembryo devejoping stages,the hasal suspensor cell and chalazal endosperm cell grow to a considerablesize. The nucleus and cytoplasma stain densely. Sometimes,bi-or trinucleate was observed inboth of the two cells. In the laterally concave embryo stage,they begin to degenerate whichcoincides with the cellularization of the endosperm. They are presumed to participate in thenourishment of the embryo proper in the early stages of embryo development.