SPERMATOPHYTES 191 



Sporophyte. The sporophyte body consists of a tuberous or columnar 

 stem, covered by an armor of leaf bases, and bearing a crown of large 

 branched leaves and an apparently terminal strobilus (figs. 433-437). 

 All the stems are tuberous when young, but in some species the tuberous 

 body passes 'into the columnar, which in certain species of Cycas reaches 



FIG. 434. Dioon edule (Mexican). After CHAMBERLAIN. 



a height of 10 or even 20 m. (fig. 433). In those forms with the per- 

 sistently tuberous habit, the stem is sometimes subterranean and very 

 small (fig. 437). While the stem usually appears to terminate in a 

 single strobilus, the strobili are in fact lateral, although close to the 

 apex, and a succession of them may appear near the stem tip. In fact, 

 in an African form strobili have been observed arising in a cycle about 

 the vegetative point. It will be remembered that the strobili of Ben- 



