OR APPENDAGES OP PLASTTS. l8iV 



plants whose hairy coats exude a viscid moisture* 

 But the hairs which clothe many plants are merely a 

 protection against cold, heat, or insects. Sometimes 

 they are hooked, sometimes branched and entangled^ 

 as in Mullein, Verhascum^ t. 549, &Cd In Croton, So- 

 lanum, and Lavatera, they have often a starry figure^ 

 Very generally they are found, under a microscope, to 

 be curiously jointed. Some Begonia bear on their* 

 leaves flat little straps called by their authors ramentct 

 shavings, instead of cylindrical hairs ; but I know not 

 that they at all differ in nature from the usual pubes- 

 cence, nor do they merit to be particularly distinguish-- 

 ed. Some of the natural order of asperifolice, as 

 Echiiwiy t. 181, and Lycopsis, t. 938, especially 

 some exotic species of this order, are clothed with 

 curious hard tubercles from which their bristles pro- 

 ceed. Echium pyrenaciiim^ Desfont. Atlant. v. 1. 

 164, is an instance of this,yi 125. 



The pubescence of plants varies greatly in degree 

 according to differences of soil or exposure ; several 

 kinds, as Mentha hirsuta^ t. 447, 448, naturally hairy^ 

 being occasionally found smooth, but if transplanted 

 they soon resume their proper habit. Yet the direc= 

 tion of the hairs or bristles proves a very sure means 

 of distinguishing species, especially in the genus 

 Mmtea, the hairs about whose calyx and flower-stalk 

 point differently in different species, and I have found 

 it the only infallible distinction between one Mint and 

 another. See Trans, of Limi. Soc. v. 5. 171. The 



accurate Dr. Roth has lately applied the same test t0 

 z 



