STEMS 



225 



FIG. 192. A scarlet runner bean, showing leaf- 

 bearing nodes, internodes, and axillary branches. 



their leaves, and this 

 is a measure of the 

 power of the inter- 

 nodes to elongate. It 

 is evident that leaves 

 separated by the inter- 

 nodes to such an ex- 

 tent that they do not 

 shade one another are 

 in the most favorable 

 condition for work. 



In such a stem, the 

 leaves begin to form before the internodes begin to elongate, 

 so that the young leaves are packed together in the structure 



called a bud; that is, a leaf- 

 bud as distinct from a flower- 

 bud. When the internodes 

 begin to elongate, the bud is 

 said to " open," and this 

 opening goes on until all 

 appearance of a bud is lost. 

 While the bud is opening the 

 young leaves become more 

 free and continue their de- 

 velopment, so that when the 

 internodes have reached their 

 full length, the young stem 

 (or branch) bears developed 

 leaves, and the plant is said 

 to be "in foliage." The pic- 

 ture of leaves developing on 

 a stem, therefore, is not that 



of an elongating stem putting out leaves, but that of an 

 elongating stem separating growing leaves that have been 

 "put out" by the nodes. 



FIG. 193. The so-called "wedding 

 smilax," showing branches that re- 

 semble leaves arising from the axils of 

 minute scales that are the real leaves. 



