CYCADALES 



iSS 



several archegonia, but soon become twisted together, so that what 

 appears to be a single suspensor is composed of two or three or more 

 suspensors in its upper portion, each terminated by an abortive embryo, 

 while beyond the region of abortive embryos stretches the single suc- 

 cessful suspensor with its embryo. It is this twisting together in the 



upper part that makes the ^ 



whole structure look like I J ^^ 



one suspensor with several 



eggs at one end and a 



single embryo at the other. 



During these stages the 



tissue in the archegonial 



region disorganizes, so that 



there is formed a large 



cavity which later becomes 



packed with the tortuous 



suspensor. 



The single successful 

 embryo rapidly invades the 

 endosperm, and for a time 

 increases in size with little 

 internal differentiation. At 

 the base of the embryo there 

 develops a conspicuous and 

 peculiar structure, the 

 coleorhiza, and at the oppo- 

 site end the stem tip and two 

 cotyledons, while the root 

 appears rather late (fig. 

 i86). 



Figs. 187-194. — Ceratozamia mexicana: em- 

 bryo and germination of the seed; figs. 187, 

 188, normal embryos with a single lateral coty- 

 ledon; Xs; fig. 189, embryo with two cotyledons, 

 from seed which had been on a clinostat during 

 the entire period of cotyledon development; X8; 

 figs. 190-194, successive stages in germination; 

 X}; in all figures, c, cotyledon, cl, coleorhiza; 

 I, scale leaf; /, first foliage leaf; r, root; s, sus- 

 pensor. — After Sister Helen Angela (58, 59). 



The usual number of 

 cotyledons is two, but three united throughout their entire length 

 have been found in Encephalarios (71). In 1879 Warming (9) 

 described the single peculiar cotyledon of Ceratozamia, and an 

 examination of abundant material from the field confirms the 

 description, but Sister Helen Angela (58) noticed that the 

 strobilus disintegrates and frees the seeds before the cotyledon has 



