90 PLANT LIFE 



Since in most cases lateral buds have a definite relation to 

 the leaves, the shoots which arise from them will have a 

 similar relation. But, since many buds are produced which 

 never develop into branches, this relation is often obscure 

 and difficult to see. 



109. Special forms. — The primary shoot may'grow under- 

 ground, in which case its stem usually takes a horizontal 

 direction and becomes much thickened for storage of reserve 

 food (•; 236), while its leaves are so reduced as to be scarcely 

 recognizable. Such a shoot is known as a rhizome. When 

 the primary stem is short, erect, and crowded with thickened 

 leaf bases it forms a bulb, as in the hyacinth and onion. 

 When the primary stem is short and thick, and has thin scale 

 leaves upon it, it forms a conn, as in cyclamen and Indian 

 turnip. 



Branches of the specialized primary shoot may be like it, 

 as when some branches of the rhizome or corm are them- 

 selves rhizomes or corms. Others, however, will be adapted 

 to other purposes, as when aerial branches arise from rhizomes 

 to carry foliage and flowers, or when slender leafless shoots 

 called runners develop from the main axis of the strawberry 

 (fig. 297). Offsets and stolons (figs. 296, 369) are similar 

 branches likewise adapted to propagation (^[ 366). 



Branches of the secondary shoots may also be different 

 from their parent axis. In different plants the shoots assume 

 the most varied forms. 



Such specialized branches may be confined to a definite 

 region of the plant, or may he distributed over it. The 

 more important of these kinds of branches may now be 

 enumerated. 



110. (a") Dwarf branches. — It is not uncommon to find 

 branches specialized merely by their slight development in 

 length and their capacity for being separated readily from 

 the parent shoot. Such short branches are particularly com- 



