FOLIAGE LEAVES: FDNCTIOX, STEL'CTUEE, ETC. 47 



3S, 39, 40, is:, 1S9, 190, 191). 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 



sbowing the ribbed stem, tlie strong spiues, and the entire 

 absence of le;ives. 



11). In all these cases this reduced surface is supple- 

 mented by palisade tissue, very thick epidermal walls, and 

 an abundant cuticle. 



3". Rosette arrangement. — The rosette arrangement of 

 leaves is a very common method of protection used by 



