606 THE GLACIAL LAKE AGASSIZ. 



occasioual groves. The greater abuudauce of tiniber on the southwestern 

 bkiffs appears to be due to their being less exposed to the sun, and there- 

 fore more moist, than the bhitfs at the opposite side of the valley. Above 

 Montevideo the timber is mainly restricted to a narrow belt beside the river 

 and to tributary valleys and ravines. 



PKAIRIE GRASSES AND FLOWERS. 



Among the fifteen hundred, more or less, indigenous species of herba- 

 ceous plants inhal)iting the Red River Ijasin, probably half are deserving of 

 note for attaining their geographic limit upon this area, or at least the 

 limit of their abundant or frequent occurrence. But thorough and detailed 

 botanic exploration of all the great interior region of our continent west- 

 ward to the Rocky Mountains and far northward will be requisite before 

 we can speak Avith certainty concerning many of the less conspicuous 

 species of our flora. We may here notice briefly some of those plants 

 whose geographic range is best known, especially such as are useful for 

 pasturage and hay. 



In general, the flora of the prairie area of Lake Agassiz is mostly made 

 up of species that are familiar to residents of the Eastern and Southern 

 States, occurring also commonly or abundantly there; but many of these 

 plants reach their western and northern limits along the Red River of the 

 North. 



On the other hand, seventy-six species^ of northern range, some of 

 them plentiful beneath the Arctic Circle, are known to extend south of the 

 forty-ninth parallel in the Red Jviver Valley, or on the east to the Lake of 

 the Woods or into northern Minnesota, but not to the southern end of this 

 valley at Lake Traverse. This northern element of the Red River flora 

 includes thuleen species of Carex, and nine grasses, the latter being De- 

 yeuxia langsdorffii Kunth, Trisetum suhspicatum Beau v., var. moUe Gray, 

 Danthonia intermedia Vasey, Poa alpina L., P. laxa Hsenke, Agropyrwm 



' Lists of these siiecies and of the western species extending into this district, also a list of the 

 weeds (troublesome to the farmer) observed in the district, both indigenous and introduced, with notes 

 of their range and relative abundance, are given in my paper, "Geographic limits of species of 

 plants iu the basin of the Red River of the North," Proc, Boston Soc. of Nat. Hist., Vol. XXV, 1890, 

 pp. 140-172. 



