CYCADALES 7 



imler, and the iimcilnge canals passing- on to join the cortical 

 canal system. 



The xylem elements are of the general Gynmosperm cliarac- 

 ter. They are all tracheitis, the first formed being spiral in 

 type anil tlie later sealariform; while in the tracheids of the 

 secondary xylem the characteristic bordered pits appear, or 

 a mixture of sealariform and reticulate thickenings may be 

 developed, as in Zainin. ]\Incilage ducts are common in all 

 organs, and the pith is also remarkably rich in stored starch. 



TJIE LEAF 



The alternation of rosettes of scale leaves and foliage leaves 

 near the aj^ex of the stem is a conspicuous feature. According 

 to Goeljel, every year or every other year a rosette of foliage 

 leaves is expanded, in the center of which is a terminal bud 



FHi. 



Cross section of u leaf of C'l/cas reoolnta. 



invested by numerous scale leaves imder whose protection a new 

 rosette of foliage leaves slowly develops (Fig. 1). In the green- 

 house material we have examined there are no such regular peri- 

 ods of unfolding. The alternation is still more striking when 

 sporopliylls are included, scale leaves, foliage leaves, and sporo- 

 pliylls being the order of succession. 



The scale leaves are brown and dry. The foliage leaves are 

 pinnate and leathery, and generally de\'olop expanded, but in 



