30 



EMBRYOGENESIS IN PLANTS 



a very early stage in the embryogeny, the relation of the distal to the 

 basal region of the embryonic axis is essentially the same as in a normal 

 adult shoot. A growing body of experimental evidence supports the 



Fig. 7. Gradient of cell size in the embryonic development 



A, Delesseria ruscifolia, red alga, germling (after Nienburg). Notothylas sp., Antho- 

 cerotales, young sporophyte (after Lang). C, Lycopodium selago; et, suspensor, 

 /, foot, a, apex (after Bruchmann). D, Lycopodium cernuum, the enlarged cells of 

 the foot in contact with the prothallus contain starch grains (after Treub). E, Os- 

 munda cinnamomea, showing the large cells of the foot,/, and the smaller cells of the 

 embryonic distal region (after Cross). F, Ginkgo biloba, young embryo (after Lyon). 

 G, Zea mays, young embryo (after Randolph). 



view that the shoot apex is a self-determining, morphogenetic region: 

 the data given above indicate that this relationship is established at an 

 early stage in the embryogeny. 



On further growth, the apex of an endoscopic embryo bursts out of 



