CHAPTEE XXYI. 
VARIATION BY ENVIRONMENT. 
Environment is a term that embraces all things 
about us which affect our being. Light, air, earth, 
and water have their influence upon us. To put it 
categorically. Do climate and surface modify the 
bodies of animals and plants ? 
Many illustrations of the effect of environment 
have been noticed. Beginning with very common 
ones, I shall take the homely smartweed. This grew 
in abundance in a small valley near my home. During 
the spring and early summer there was considerable 
water in the ravine. The smartweed grew rank 
there; it had smooth stems and leaves. When the 
summer heat dried up the water, the stems developed 
tiny hairs. After several weeks of rainy weather 
these would again disappear. 
Another species of the smartweed family has long 
stems bearing smooth obtuse leaves with stomata on 
the upper surface. When this plant grows out of 
water the stem is short, and is covered with downy, 
lanceolate leaves with stomata on both sides. 
The terrestrial species of the buttercup develops a 
hairy scape and a felt-like surface on the upper side 
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