Minnesota Plant Life. 



21 I 



tribiition, wliile tiiml)ling grasses — after they have ripened their 

 seeds — separate their flower-clusters, bring them together into 

 balls and permit the wind to roll them over the plains or 

 meadows. 



Mat-grasses and dune-grasses. A few grasses take the form 

 of what are known as mat-plants or carpet-plants. These are 

 found in w^aste fields and the plant-body has a marked prostrate 

 appearance, lying flat upon the ground and producing, if unin- 

 terfered with, a circular disc a foot or more in diameter. Such 

 vegetation-forms could not very well arise in the forests or in 

 marshes, but are charac- 

 teristic of open, sandy 

 fields. Peculiar varieties 

 of grasses are usually 

 found on sand-d u n e s . 

 These, of which the wild 

 rye is a conspicuous ex- 

 ample, have a luxuriant 

 subterranean body made 

 up of rootstocks and 

 roots by which they bind 

 the sand together — hence 

 they are known as sand- 

 binding grasses. The 

 planting of grasses of this 

 sort where sand-dunes 

 show a tendency to en- 

 croach inland, is often 

 suf^cient to stay the ad- 

 vance of the dune. In France such grass-planting is employed 

 by the inhabitants along the coasts of Brittany to prevent the 

 beach sand from being blown continuously in shore. In north- 

 ern Indiana, between Chicago and Elkhart, there is an area 

 where the sand of Lake Michigan has been blown inland for 

 many miles, covering the soil and by its thick drifts making val- 

 uable farms worthless. In such positions considerable growths 

 of wild rye would serve to bind the sand and raise a barrier to 

 its farther encroachment. 



Fig. 92. Cyperus-sedge. After Britton and Brown. 



