94 



BUDS A^D STIPULES 



The development of such glandular hairs in Lilac is 

 shown in figs. 137-139. A cell raises itself somewhat 

 above the general level of the leaf, and becomes cut off 

 by a transverse wall (fig. 137, a, fr; fig. 138, a). It 

 then divides into two transversely, the upper cell form- 

 ing the head of the pin (fig. 138, fr), which may divide 

 again by vertical and transverse walls (fig. 139). 



As a general rule special hairs develop themselves 

 into glands. In the Plane (figs. 140, 141), however, we 

 find a remarkable combination of the two. The hairs 



FIG. 139. 



DEVELOPMENT OF STALKEI> GLANDULAR SECHETING HAIKS IN 



LILAC (Syringa vulgaris). 

 In fig. 139, ft, the stalk has not been formed. 



branch, and one fork may remain a simple pointed hair, 

 while another develops a gland. 



The glandular processes are sometimes highly deve- 

 loped; as, for instance, in the Eose and the Violet, 

 where they are large and oval, one being formed at the 

 tip of each tooth of the leaf. 



In the Docks (Rumex), Polygonum, and Rhubarb 

 (Rheum) the buds secrete a copious mucus, which in 

 some of the larger species can even be squeezed out 



