114 



MORPHOLOGY OF GYMNOSPERMS 



and that it is not a symbiont, but rather a parasite against which the 

 cell reacts as a phagocyte. 



2. The spore-producing members 



THE MICROSPORANGIUM 



All the living cycads are strictly dioecious. The staminate strobili 



usually occur singly in the 

 center of the crown (fig. 95), 

 but several may appear at 

 once, as is frequently the case 

 in Zaniia and Encephalartos. 

 The first cone produced by a 

 plant is always terminal, but 

 all subsequent ones are lateral. 

 Growth from an apical meri- 

 stem is continuous until a cone 

 is produced, in which case the 

 meristem is used up in the pro- 

 duction of the cone, and a new 

 meristem appearing at the base 

 continues the growth, pushing 

 aside the cone and assuming 

 the erect position. Miss F. 

 Grace Smith (56) has shown 

 that the trunk of Zamia is 

 really a sympodium, the pro- 

 duction of a cone being fol- 

 lowed by the development of 

 a branch which quickly be- 

 comes erect, so that the trunk 

 does not appear to be branched 

 (figs. 96-98). In Encephal- 

 artos Friderici-Guilielmi and 

 in E. AUensteinii Pearson 

 (47) has described a group of 

 Fig. 05.— D/oo«e</z</e; upper portion of three to six cones arranged 

 plant uith staminate cone; photographed at symmetrically about the apex, 



Chavarrillo, Mexico, September 1906; one- . 



third natural size— After Chamberlain (63). SO that in these cases there IS 



