132 



ROOTS AND UNDERGROUND STEMS 



ground there is little danger of mistaking its identity, even 

 when it puts forth roots from every node, like the creeping 

 stems of Bermuda grass and couch 

 grass. Even in such underground 

 stems as those of the mint and couch 

 grass their real nature is evident from 



273. Rootstock of creep- 

 ing panic grass. 



272. Running rootstock of peppermint (GRAY). 



the regular nodes into which they are 



divided, and the scales which they 



bear instead of leaves. Stems of this 



kind are called rootstocks. They 



usually send out roots from every 



node and are the most ineradicable pests the farmer has 



to contend with, since each joint is capable of developing 



into a new plant, and chopping them to pieces serves only 



to aid in their propagation. 



189. Rhizomas. Rootstocks do not always retain their 

 stemlike nature so plainly, but are commonly more or less 

 shortened and thickened, as in the violet, iris, bulrush, 

 sweet flag, bloodroot, etc., and it is to this condition that the 

 name rhizoma is usually applied. A typical example of 

 the rhizoma is that of the Solo- 

 mon's seal (Fig. 274.) The pecul- 

 iar scars from which it takes its 

 name are caused by the falling 



274- -Rhizoma of Solomon's awav eac h year o f tne flowering 

 seal (after GRAY). 



stem of the season, after its work 



is done, leaving behind the joint or node of the under- 

 ground stem from' which it originated. Thus the plant 

 lives on indefinitely, growing and increasing at one end 

 as fast as it dies at the other. The joints on the rhizoma 

 mark, not the age of the plant, but of each joint or 

 internode. If there are two or three joints, this indicates 



