95 



Fig. 186. The Dragon Tree of Teneriffe 

 (.Draccmux Draco). 



branch again developes two other buds at its apex in like man- 

 ner, and this mode of growth is continued with the successive 

 branches, which are therefore also forked. In other Endogens 

 we have lateral buds formed as in Exogens ; this is the case in 

 the Asparagus, in the Screw Pine (Jig. 178, 2), in the Dracanas 

 (Jig. 186), &c. As the lower part of such stems receives more 

 vascular bundles than the upper they are necessarily larger in 

 their diameter at that part, and thus these stems are conical or 

 taper upwards like those of Exogens. 



Some Endogens present an anomalous structure ; thus in 

 most Grasses the stem is hollow (Jig. 187), except at the points 

 where the leaves arise, at which parts sohd partitions are formed 

 across the ca\ity, by which it is divided into a number of sepa- 

 rate portions. Such stems when examined at their tirstdeve- 

 lopment present the usual appearance of Endogens, but in 

 consequence of their growth in diameter taking place more 

 rapidly than new matter can be deposited in their interior, they 

 soon become hollow. 



In some other Endogens we have a more striking deviation 

 from the ordinary structure. Thus the Sarsaparillas and a 

 few other allied plants have aerial stems which are strictly 

 endogenous, and underground stems which have the vascular 

 bundles arranged in one or two zones surrounding a central 

 cellular substance (Jig. 188), like the wood around the pith 



