* 
Test against it, but it is certain that all other theories are’ ul- 
342 A. Winchell on the Prairies of the Mississippi Valley. 
verdure clothed everywhere the more ancient surface of the 
rift; and here and there in the abandoned lake bottom, rose a 
knoll crowned with its emerald crest—an island perhaps in the 
former lake. Thus the prairies were at first a naked and herb- 
less waste. . 
6. The vegetation which finally appeared on the drained lacustrine 
areas was extra-limital, and was more likely to be herbaceous than 
arboreal, 
agencies, and especially the two more important ones, w 
effect the distribution of any except the smaller and lighter 
soil; an 
would be able to plant itself along the belt thus destined to be- 
come the “ barrens.” : 
hus the prairies were treeless because the grasses first gained 
foothold and then maintained it. The Indian, perhaps, made 
his appearance at this time, and formed an alliance with the 
grasses in their contest against the trees; and thus decided the 
question in favor of the grasses. 
: ‘This is our theory of the origin of the prairies, and the 
ence of trees from their surface. Fatal objections may 
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