﻿1903] EMBRYOGENY OF ZAMIA 1 85 



quite normally, a large proportion of the ovules becoming seeds 

 with fully formed embryos. The material yielded a fairly com- 

 plete series of stages from a period somewhat before fertiliza- 

 tion to the ripening of the seeds. 



The presence of a ventral canal cell among the C3'cadales 

 was for some time in question. Strasburger (2) seems to have 

 been the first to recognize it in 1876 in Cycas sphaerica, and in 



Warm 



canal cell in Ceratozamia 



robusta, but soon (4) decided that he had been mistaken. In 



1884 Treub (5) failed to find one in Cycas circi?uilis, and the 



impression became general that no such cell is formed among 



Cycadales. In 1896, however, Ikeno (6) announced that a 



ventral canal cell is formed in Cycas revoluta, and in a later 



paper (8) he figured and described the mitosis that separates the 



nuclei of the ventral canal cell and egg. In 1897 Webber (7) 



reported that in Zamia "a small cell is cut off at the apex of 



the archegonium, which corresponds to the canal cell of Con- 

 ifers." 



In our study of Zamia the mitotic figure was found which 

 gives rise to the nuclei of the egg and ventral canal cell {Jig. /). 

 The chromosomes are very slender and inconspicuous, and the 

 spindle is somewhat multipolar. Considering the great size of 

 the central cell, the whole structure is extremely small and 

 might easily escape notice unless well stained. After the mito- 



sis is completed the nucleus of the egg begins to enlarge and to 



move toward the center of the cell, while the other nucleus 



(Jig. 2). It will be seen 



/. 



between the two nuclei, and we 



were not able to find any case in which a definite ventral canal 



cell had been cut off. 



The protuberance in which the ventral canal nucleus lies rap- 

 idly disorganizes and remains for a time as a more deeply stain- 

 ing mass at the top of the tgg. It seems probable that in his 

 first account Warming (3) was describing as a ventral canal cell 

 the disorganizing protuberance in which the ventral canal 

 nucleus lies. Ikeno's fig. 11 (8) seems to be almost identical 



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