EXTERNAL CHARACTERISTICS 



213 



Cabbage and tulip leaves show this bloom and you have 

 doubtless noticed it on the skins of grapes. 



A plant surface covered with soft hairs is said to be 

 pubescent; the skin of a peach furnishes a familiar example 

 of pubescence. Many leaves are slightly pubescent, usually 

 more so on the under side than on the upper. Some leaves 

 are densely pubescent, the leaves of the common mullein 



Fig. 76. — A leaf mosaic formed by the leaves of the Japanese ivy. 



of the pastures being an example. The dense hairs of 

 mullein leaves may have something to do with the mistaken 

 tradition of boyhood that when they are dried they are 

 good to smoke. The stinging hairs of nettle, and the 

 stiff, spine-Hke outgrowths of thistle leaves are also f amihar. 

 These epidermal hairs of leaves when examined under 

 the microscope often are found to have strange and sym- 

 metrical forms; some are stellate (star-shaped) and quite 

 beautiful. (See Figure 77.) 



