116 ELEMENTS OF BOTANY 
the cactuses (Fig. 81), and the green outer layers of the 
stem do the work of the leaves. 
137. Rolled-Up Leaves. — Leaves which receive but a 
scanty supply of water are often protected from losing it 
Fic. 80. Xerophytic Leaves of Australian Blackberry. 
J, leaflets reduced in many cases to bare midribs, in other cases showing a bit 
of blade at the end; P, petiole. 
too rapidly by being rolled up, so that the evaporating, 
z.e., stomata-containing, surface is on the inside of the 
roll. Sometimes, as in the crow-berry (Fig. 82), the curled 
