CHAP. II. PUBESCENCE. 79 



disappear altogether, one would have been apt to 

 think it unfit for the purposes of specific discrimi- 

 nation. But botanists have not scrupled to accept 

 of its assistance in cases of necessity, as well as of 

 that of the prickle, which is indeed permanent. The 

 former has been employed with success in the genus 

 Primus, and the latter in the genus Rubus. 



2. Plants that are furnished with strong and nu- 

 merous thorns, as they are well calculated, so they 

 are often used, for the purpose of inclosing by quick- 

 set fences. Hence the utility of the Sloe, Haw- 

 thorn, Furze, and Holly-tree, forming when well 

 trained a fence both durable and ornamental. In 

 some species of Mimosa the thorns are so strong 

 and thick set as to form a defence altogether impe- 

 netrable to the attacks of animals, except, perhaps, 

 the rhinoceros ; which is the less to be wondered 

 at, as his skin is not only thicker and harder than 

 that of the elephant, but is even said to be mus- 

 ket-shot proof. 



SECTION VII. 

 Pubescence. 



THE pubescence is, a general term, including un- Defini- 

 der it all sorts of vegetable down, or hairiness, with tl 

 which the surface of the plant may be covered, 

 finer, or less formidable, than the armature. 



Some plants have their surface wholly smooth Micros* 



copical. 



9 



