THE ANGIOSPERMAE 



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Fig. 1 3 18. — A-F, Schematic derivation of the angiospermic 

 embryo sac from the female prothallus of the Gymno- 

 spernis. A, Sequoia type. B, Cupressacean type. 

 C, Ephedra tvpe. D, Hypothetical type without arche- 

 gonial jacket layers. E, Type reduced to two archegonia 

 with two neck cells. Ventral canal nuclei separated from 

 archegonia. F, Angiosperm type, with two archegonia 

 at opposite ends of the sac. 1-4, Development of a 

 gvmnospermic archegonium. 5-8, Development of the 

 angiospermic egg-apparatus, for comparison. (After 

 Porsch.) 



forward another theory, but as it chiefly concerns the origin of the endo- 

 sperm, we will postpone its consideration until after we have dealt with 

 fertilization. Against Berridge's objection may be urged the known cases 

 in Gymnosperms in which the ventral canal nucleus is actually fertilized by 

 the second male nucleus, e.g., in Abies, Thuja and in two species of Ephedra. 

 In some other genera the ventral canal cell divides and gives rise to a small 

 mass of tissue, probably as a consequence of such fertilization. 



Porsch's theory has also been attacked by Battaglia on the ground that 

 variability in the formation and behaviour of the cells of the egg-apparatus 

 precludes comparison with an archegonium. Further, he argues that the 

 N* 



