30 



MORPHOLOGY OF SPERMATOPHYTES 



organ and later became used as a sperm carrier, or whether 

 the reverse is true. It would seem natural to think of the 

 Cycad condition as the more primitive one. 



IV. THE EMBRYO 



The first comparatively full account of the development of 

 the embryo is that given by Treub 14 for Cycas circinalis, and 

 this account has been confirmed by fragmentary observations 

 The account given by Ikeno 28 for Cycas revoluta agrees 



since. 



FIG. 26. Cycas circinalis, development of the embryo: A, an ovule from above, show- 

 ing the openings of the necks of several archegonia, x % ; B, longitudinal section 

 of'an archegonium, x 73; (7, a fertilized egg, showing several free nuclei, x 24; 

 D, free nuclei of the proembryo, showing parietal placing, x 36 ; E, a young pro- 

 embryo, x 15; F. a young embryo, showing saclike proembryo, suspensor (susp), 

 and embryo proper (), x 6; G, longitudinal section of seed containing two embryos, 

 two thirds natural size; If, embryo with suspensor, x 1%; </, a more advanced em- 

 bryo, two thirds natural size ; K, a mature embryo. After TREUB (from Engler and 

 Prantl's Nat. Pflanzenfam.). 



in every particular with Treub's, and fills in certain gaps. 

 There is still almost entirely lacking any knowledge of the devel- 

 opment of the embryo itself. The embryogeny shows three dis- 

 tinct phases as follows (Fig. 26) : 



1. Development of Proembryo. This name was applied 

 by Treub to the intrasporic development. The oospore en- 

 larges, continuing to receive supplies of nutrition from the adja- 

 cent tissue. The first change observed by Treub was the pres- 



