THE LEAVES. 



121 



152. Stipules.- -The leaf base frequently branches. These 

 branches, commonly two in number, are called stipules (fig. 

 138). They vary from slender, awl-shaped bodies to flat- 



FIG. 138. A growing shoot of a thorn (Cratcegus punctata). n, leaves developed as 

 bud scales which protected the parts above when in the bud ; S, stipules. Natural 

 size. After Reinke. 



tened and leaf-like ones. The stipules may remain attached 

 to the base throughout the life of the leaf, or may fall away 

 early. Usually the two are separate, but they may be united 

 with the leaf base itself, forming wings for it, as in roses 

 (fig. 139), or they may be united with one another so as to 

 form a sort of sheath encircling the stem (fig. 140). When 

 the leaf base is winged, the wings extend downward as lobes 

 more or less encircling the stem. In many cases the leaf is 

 said to be clasping (fig. 141). These lobes may even unite 

 on the other side of the stem, so that the stem seems to 

 penetrate the base of the blade. (See fig. 142.) When two 

 leaves occur at the same node, corresponding lobes of the 



