PROTECTION AGAINST DROUGHT — 37 
highly impervious skin, so that they act as veritable 
cisterns. In plants like the Cacti water storage in the 
stems is carried very far indeed; while in such genera 
as the Stonecrops (Sedum) the leaves are often so 
swollen and charged with water that they lose up to 
Fic. 4.._WiLpD Carrot (Daucus CaRoTA), GROWING 
UNDER GREAT EXPOSURE, }4. 
98 per cent. of their weight if they are dried. Preven- 
tion of excessive loss of water by transpiration is 
effected in plants of dry places mainly by reduction in 
the size of the leaf and by protection of its surface. 
Leaf reduction is very marked in many dry countries. 
If we compare the flora of the Mediterranean region 
