228 OP THE FULCRA, 



The pubescence of plants varies greatly 

 in degree according to differences of soil or 

 exposure ; several kinds, as Mentha hir- 

 suta, t. 447, 448, naturally hairy, being 

 occasionally found smooth, but if trans- 

 planted they soon resume their proper habit. 

 Yet the direction of the hairs or bristles 

 proves a very sure means of distinguishing 

 species, especially in the genus Mentha, the 

 hairs about whose calyx and flower-stalk 

 point differently in different species, and 1 

 have found it the only infallible distinction 

 between one Mint and another. See Trans, 

 of Linn* Soc. v* 5. 171. The accurate 

 Dr. Roth has lately applied the same test 

 to the species cf Myosotis, which all bota- 

 nists before him had either confounded 

 under M. scorpioides, Engl. Bot. t. 480, 

 or else separated upon vague principles. 

 Some species of Galium are admirably 

 characterized by the bristles of their leaves, 

 or of parts of their leaves, being hooked 

 backward or forward. We therefore ac- 

 ceptthe 272d maxim of Linnseus's Philoso- 

 phia Botanica with that limitation which 

 he himself has allowed in his commentary 



