EMBRYOGENESIS IN FLOWERING PLANTS 



229 



right-angles to the axis of the developing germ. Free nuclear division, as 

 in the proembryo phase in gymnosperms, has not been reported in the 

 angiosperms. In the two-celled embryo, the cell next to the micropyle is 

 known as the basal cell, and that which projects into the embryo sac as 



Fig. 53. Capsella bwsa-pastoris 

 A classical example of embryogeny in a dicotyledon. Stages in the embryogeny 

 illustrating Soueges' system of analysis and nomenclature {see also Fig. 55). The 

 first transverse wall divides the zygote into an apical and a basal cell, ca and cb 

 respectively. The products of these two cells and their respective contributions to 

 the embryonic development are indicated; e, embryonic cell; su, suspensor; hy, 

 hypophysis; s, position of shoot apex (semi-diagrammatic, after Soueges). G, 

 Chelidomitm majits. Different types of proembryo at the six-cell stage (after Soueges). 



the terminal cell. The diversity in the early embryogeny of dicotyledons 

 and monocotyledons depends largely on the nature of the further 

 development of these two cells. The basal cell (i) may remain undivided 

 with or without subsequent enlargement, or (ii) it may undergo further 

 transverse divisions either {a) contributing to the embryo proper, or 



