THE GREAT AMERICAN DESERT 



22( 



one half miles wide by five miles long. They vary in depth from four 

 feet to probably about twenty-five feet. In many of the fresh water 

 lakes the vegetation is encroaching upon the water, so that in time all of 

 the lakes will have disappeared and wet meadows remain. The wet 

 meadows of to-day show this sort of an origin very plainly. Many stages 

 in lake eradication by invading vegetation may be seen in these lake 

 regions. Some lakes are quite free from submerged aquatic plants; 

 others quite free from bulrushes or wild rice ; others show belts of these 

 plants about the shore; in others the bulrushes have begun to wander 



Fig. 13. Some of the Lakes are so Strongly Alkaline that the Salts 

 Coat the Beach with a White Crust. 



into the deeper water, and in still older lakes the water can not be seen 

 because of the complete occupation by the bulrushes and other vegeta- 

 tion. The bulrush is the commonest pioneer in this succession, and it 

 is well fitted for this particular process. Oddly enough it is by the 

 possession of the rhizome type of propagation, the very same character 

 that fits RedfieJdia for capturing the blow-out, that the bulrush is 

 enabled to thus encroach upon the open water and finally to capture 

 the lake. In the one case we have a species successfully eradicating a 

 very dry, unstable habitat and in the other case a different species 

 eradicating a very wet, stable habitat by identically the same means. 

 The creeping rhizomes of the bulrush keep reaching into deeper water 

 as the lake bottom is built up until other species are enabled to gain a 

 hold back of the rushes. Thus other species follow in the wake of the 

 bulrushes, and then come the common wet meadow species. At last 

 the water is gone, the aquatic plants are gone, the bulrushes are gone, 

 and the wet meadow plants have full possession of the former lake area 



