252 BOTANICAL GAZETTE [march 



a later stage in which the embryo has attained its full length, has 

 broken the seed coat, and pushed out the dried remains of the 

 suspensor and archegonial wall. 



The embryo at this stage consists of cotyledons, plumule, and a 

 basal part which in its upper portion is hypocotyl, and in its lower 

 portion root sheath; for the root is endogenous, and is not pre- 

 ceded by any structure which might be looked upon as a ''radicle" 

 or "caulicle." The hypocotyl is extremely short, and the distinc- 

 tion between it and the root sheath cannot be determined super- 

 ficially, but only by study of the internal structure. The number 

 of cotyledons varies from 2 to 4, and all stages of their union are 

 represented (figs. 20-22, 24). 



The vascular cylinder of the hypocotyl is a protostele. It has 

 4 easily recognized protoxylem groups, in no way differing from the 

 h3Apocotyl cylinders of Ceratozamia'^ and Microcycas.^ The coty- 

 ledons are multifascicular, like those of Ceralozamia and Microcycas, 

 and unlike those of Zamia and Dioon ediile. In the embryos which 

 are dicotyledonous, the manner in which the cotyledonary traces 

 are supplied from the hypocotyl cylinder is exactly the same as 

 that described by Thiessen^ for Dioon edule, and which Coulter 

 and Chamberlain^ have shown to be characteristic of the cycads. 

 When the embryo has 4 cotyledons, each cotyledon is on a side of 

 the quadrangular node, and receives a secondary bundle from each 

 of the adjacent angles. Twelve out of 100 embryos had 4 coty- 

 ledons, and in each case the vascular strands arose in this manner. 

 In the tricotyledonous embryos (there were 4 of them in 100), one 

 of the 3 cotyledons was supplied in the dicotyledonary manner, and 

 the other two after the manner of the embryos with 4 cotyledons; 

 and yet, at a level just above the tip of the plumule, the number of 

 vascular strands was about equal in the 3 cotyledons. The strands 



■• DoRETY, Helen A., The seedling of Ceralozamia. Box. Gaz. 46:203-220. 

 pis. 12-16. 1908. 



5 , Vascular anatomy of the seedling of Microcycas calocoma. Bot. Gaz. 



47:139-147- pis. 5,6. 1909. 



* Thiessen, Reinhardt, The vascular anatomy of the seedling of Dioon edule. 

 Bot. Gaz. 46:357-38o.*'/»/5. 23-29. 1908. 



7 Coulter, J. M.,^and Chamberlain, C. J., Morphology of gymnosperms. 

 Chicago. 1910. 



