CHAP. II. PUBESCENCE. 81 



bristly, and issuing from small and white tubercles 

 imbedded in the surface of the leaf or stem, as in 

 Lycopsis arvensis and Echium vulgare. 



In their structure the hairs are generally cylindri- 

 cal but tapering to a point, as in the Vetch and 

 Mallow ; or they are awl-shaped, as in Begonia 

 nitida; or hatchet-shaped, as in the Hop; or hooked, 

 as in Agrimony. They are also either simple, as in 

 Hieracium ; or forked, as in Lavender ; or branched, 

 as in the foot-stalk of the Gooseberry-leaf; or star- 

 red, as in Atyssum ; or jointed, as in the Thistle. 



The pubescence is extremely apt to change its ap- Affected 



f -i -by cultiva- 



pearancc from soil, exposure, or culture ; in con- ^ 

 sequence of which Linnaeus regarded it as a ridi- 

 culous mark of specific distinction, except in cases of 

 absolute necessity. But these cases of necessity have 

 actually occurred ; and Sir J. E. Smith has employed 

 it with great success in the difficult task of dis- 

 tinguishing the different species of Mint ; * as has 

 also Dr. Roth-j- in distinguishing the different 

 species ofMyosotis; which, Proteus-like, had former- 

 ly eluded all sorts of attempts to subject it to the 

 chains of specific discrimination, transforming itself, 

 in its other features, into all possible shapes, but 

 constant to none. Mr. Brown has likewise em- 

 ployed it with equal success in his elucidation of 

 the Natural Order of the Proteaceae of Jussieu4 



* Trans, of Linn. Soc. vol. v. f Flora Germanic*. 



J Lin. Trans. Vol. X, Part 1. 

 VOL, I, 



