272 CONSERVATIVE ORGANS. [jLECT. VI. 



a. Scabrous (scaber), when it is thickly co- 

 vered with small papillae, which are not vi- 

 sible, but can be felt on running the finger 

 along it ; as in Black Knapweed, Centaurea 

 nigra. 



b. Warty (verrucosus) (Plate 5, fig. 6), when 

 it is studded over with small hard warts, or pa- 

 pillae, which can be both seen and felt ; as in 

 Warty Spindle-tree, Euonymus verrucosus. 



c. Vesicular (papulosus) (Plate 5, fig. 7), when 

 the roughness depends on a small elevation of 

 the epidermis containing a watery fluid, which 

 gives the plant the appearance as if it were co- 

 vered with ice ; as in the Ice Plant, Mesembry- 

 anthemum crystallinum. 



In point of FIGURE, stems are very diversified ; 

 and this is best ascertained in a transverse sec- 

 tion. When a stem is thus examined, the follow- 

 ing forms are found to exist. 



a. Round, cylindrical (teres, cylindricus*), 

 / (fig. s, l). A stem is said to be round when 

 a transverse section appears nearly circu- 

 lar, for no stem is perfectly so : and the 

 term cylindrical is employed with still 

 more latitude, for all stems gradually di- 

 minish from the base to the apex. Stra- 

 monium, Datura stramonium, and Change- 



* Teres cylindricus." Phil. Bot. 82. 12. 



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