256 



EMBRYOGENESIS IN PLANTS 



considerable endosperm formation before any development of the 

 zygote takes place. The segmentation of the embryo is somewhat 

 irregular and results in the formation of an undifferentiated ovoid, 

 bulbous embryo, with a massive suspensor which grades into the 

 embryonic region. On further growth, the ovoid embryo becomes 



em 



B 



PCQ,-. 



Fig. 63 



A, B, Grerillea robusta (Proteaceae). A, Two-celled embryo surrounded by endo- 

 sperm. B, A later stage; the embryo is now spherical; there is no suspensor (A, 

 X 300; B, X 225; after Brough). C-F, Embryos of Leguminosae. C, Rothia tri- 

 foliata. D, Sesbania aegyptiaca. E, S. graiidiflora. F, Vigna catjang (C, D, F, X 187; 



E, X 133; after Rau). 



bilobed distally, the plumule and two cotyledons become organised, 

 and a root primordium is differentiated. The two cotyledons tend to be 

 unequal in size, i.e. in width, the larger one, though single at its point of 

 conjunction with the hypocotyl, becoming two-lobed distally. In fact, 

 there is what appears to be a nascent but unrealised tricotyledonous 

 condition; this may be correlated with the general massive basis of the 

 embryonic development. According to Compton (1913), polycotyle- 

 dony is very rare in angiosperms, many of the reputed examples being 



