124 EVERGREEN LEAVES. [CHAP. 



Mr. Grindon, in his Echoes on Plant and Flower 

 Life (p. 30), says that " the occurrence of prickles only 

 here and there among plants shows them to be un- 

 connected with any general and ruling requirement 

 of vegetation. We can only fall back upon the 

 principle laid down at the outset, that they are 

 illustrations of the unity of design in Nature, leading 

 us away from the earth to Him who is ' the end of 

 problems and the font of certainties.' " Surely, 

 however, it is obvious that the existence of spines 

 and prickles serves as a protection. 



Another point of much importance in the economy 

 of leaves is the presence or absence of hairs. I have 

 already observed that most evergreens are glossy and 

 smooth, and have suggested that this may be an 

 advantage, as tending to prevent the adherence of 

 snow, which might otherwise accumulate and break 

 them down. 



The hairs which occur on so many leaves are ot 

 several different types. Thus, leaves are called silky 

 when clothed with long, even, shining hairs (Silver 

 Weed) ; pubescent or downy, when they are clothed 

 with soft, short hairs (Strawberry) ; pilose, when the 

 hairs are long and scattered (Herb-robert) ; villous, 

 when the hairs are rather long, soft, white, and close 

 (Forget-me-not) ; hirsute, when the hairs are long 

 and numerous (Rose-campion) ; hispid, when they are 

 erect and stiff (Borage) ; setose, when they are long, 

 spreading, and bristly (Poppy); tomentose, when they 

 are rather short, soft, and matted ; woolly, when long, 

 appressed, curly, but not matted (Corn-centaury) ; 

 velvety, when the pubescence is short and soft to the 



