UNDERGROUND STEMS 



179 



node, will develop a new plant. Weeds of this type are multi- 

 plied rather than destroyed by plowing and discing. 



Underground stems may be much elongated or they may be 

 short and thick. In their su})terranean habit, they resemble 



roots, and one may easily 

 mistake some types of them 

 for roots, unless the stem 

 characters are well in mind. 

 However, the presence of 

 nodes, internodes, and 

 leaves, although the latter 

 are usually scale-like, serve 

 to identify the underground 

 structure bearing them as 

 a stem. For example, the 

 so-called eyes of the Irish 

 Potato are buds and are lo- 

 cated in the axils of small 

 scales which mark the nodes 

 of the tuber. (Fig. 155.) 

 On some the scale-like 



Fig. 15-i. — A Woodbine {Ampdopsis 

 climbing a stone wall, a, tendrils. 



Fig. 155. — Irish Potato. 

 e, eyes; s, scale leaves. 



leaves are large and fleshy, while on others they are very incon- 

 spicuous. Underground stems differ so much that they have 

 been classified into rhizomes or rootstocks, tubers, bulbs, and corms. 

 Rhizomes are very much elongated underground stems. They 

 are so named because of their resemblance to roots (the word 

 rhizome meaning root-like). They are commonly called root- 

 stocks. The rhizome is one of the most common forms of under- 



