116 



ESSENTIALS OF BOTANY 



the cactuses (Fig. 81), and the green outer layers of the 

 stem do the work of the leaves. 



137. RoUed-Up Leaves. — Leaves which receive but a 

 scanty supply of water are often protected from losing it 



Fig. 80. Xerophytic Leaves of Australian Blackberry. 



I, leaflets reduced in many cases to bare midribs, in other cases showing a bit 

 of Wade at the end ; P, petiole. 



too rapidly by being rolled up, so that the evaporating, 

 i.e., stomata-containing, surface is on the inside of the 

 roll. Sometimes, as in the crow-berry (Fig. 82), the curled 



