136 MORPHOLOGY OF GYMNOSPERMS 



A ventral canal cell in cycads was first described by Strasburger 

 (7) in 1876 for Cycas sphaerica, and the next year Warming (8) 

 described one in Ceratozamia robusta, but soon concluded that he 

 had been mistaken. Treub (13) in 1884 failed to find any ventral 

 canal cell in Cycas circinalis, and from that time it was generally 

 believed that the cycads have no ventral canal cell. In 1898, however, 

 Ikeno (27) made an unmistakable demonstration of the critical 



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Figs. 145-147. — The ventral nucleus in cycads: fig. 145, Cycas revolula; mitosis 

 which produces ventral canal nucleus and egg nucleus; X375; fig. 146, Dioon edule; 

 later stage, showing that no cell plate is appearing in connection with the spindle; 

 X350; fig. 147, Dioon edule; the ventral canal nucleus disorganizing, while the egg 

 nucleus is increasing in size (no wall has been formed between the nuclei); X41. — 

 Fig. 145, after Ikeno (27); figs. 146, 147, after Chamberlain (46). 



mitosis in Cycas revolula (fig. 145), his figures showing that no wall 

 is formed between the ventral canal nucleus and the egg. Webber 

 (26) in 1897 reported a small cell cut off from the apex of the arche- 

 gonium in Zamia, but in 1903 Coulter and Chamberlain (33) 

 showed that here too there is only a nuclear division. More recently, 

 Chamberlain (46) has shown that there is a ventral canal nucleus 

 in Dioon and in Encephalartos (figs. 146, 147). The figure of Dioon 

 shows not only that there is a nuclear division that gives rise to the 

 ventral canal nucleus and egg nucleus, but also that wall-formation 

 between the two nuclei has been so completely suppressed that no 

 trace of its initiation is seen in the spindle. 



