FOLIAGE LEAVES: FUNCTION, STRUCTURE, ETC. 47 
38, 39, 40, 185, 186, 187, 188). In the same regions the 
agaves and yuccas retain their leaves, but they become so 
thick that they serve as water reservoirs (see Figs. 38, 39, 
FIG. 40. A globular cactus, showing the ribbed stem, the strong spines, and the entire 
absence of leaves. 
189). In all these cases this reduced surface is supple- 
mented by palisade tissue, very thick epidermal walls, and 
an abundant cuticle. 
37. Rosette arrangement. The rosette arrangement of 
leaves is a very common method of protection used by 
