CHAPTER XI. 
Leaves of Peculiar Forms and Uses. 
127. Leaves in Hot, Dry Climates.— In regions where the 
greatest dangers to vegetation arise from long droughts and 
the excessive heat of the sun, the leaves of plants usually 
offer much less surface to the sun and air than is the case in 
temperate climates. Sometimes the blade disappears and the 
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Fic. 88.— Leaf of Nightshade, with Midrib Fic. 89.—Spiny Leaves of 
Prickly above and below. Barberry. 
expanded petiole answers the purpose of a blade, or again, 
the leaves disappear altogether, as in the cactuses (Fig. 38) 
and the green outer layers of the stem do the work of the 
leaves. 
1 Solanum. 
