LECT. XI.] CAULINAR AND FOLIAR APPENDAGES. 639 



in some plants, as Borago laxiflora, covered 

 with warts. They are either simple or undivided, 

 or compound or branched. 



1. Simple hairs (Pili simplices). The com- 

 monest form of the simple hair is that of a jointed 

 thread generally too flexible to support itself; there- 

 fore it is more commonly found variously bent and 

 waved (Plate 9, fig. 10. a. b.)*. According to its 

 degree of fineness, its quantity and the mode of its 

 application to the surfaces of stems and leaves, it 

 constitutes the characteristics of surfaces : thus the 

 surface is termed hairy (pilosus) when the hairs are' 

 few and scattered, but conspicuous, as in Mouse- 

 ear Hawkweed, Hieracium Pilosella; woolly (lana- 

 tus), when they are complicated, but, nevertheless, 

 the single hairs are distinguishable, as in Mullein, 

 Verbascum; shaggy (tomentosus) , when they are so 

 thickly matted that the individual hairs cannot be 

 distinguished ; and when the position of the hair is 

 nearly parallel to the disk, being at the same 

 time straight or very slightly curved (Plate 9, fig. 

 10. c.), and thick although unmatted, it consti- 

 tutes the silky surface, as in the leaves of Wild 

 Tansey, Potentilla anserina; Silvery Ladies' mantle, 

 Alchemilla alpina, &c. In some instances the 

 simple hair is firm enough to support itself erect; 



* In all the figures of hairs and bristles in Plate 9, the size of 

 the appendage, when viewed with a common lens, is placed 

 beside its highly magnified representation. 



