600 MINNESOTA BOTANICAL STUDIES. 



brows of the knolls are occupied almost exclusively by an Artemisia 

 formation in which three or four species are present, Artemisia 

 frigida being the most abundant. Scrub poplars, hazel and Quercus 

 form a sparse "gallery wood." On the upland Gaillardia, Amor- 

 pha, Gaura and other xerophytic herbs and shrubs of the prairie are 

 abundant. 



PLATE XLI. 



Elm woods along the Red Lake river near Crookston, Minn. The 

 bottoms being subject to overflow, show a scanty undergrowth mostly 

 herbaceous, though with a few shrubs of Ribes, Rubus and Corylus. 

 In such glades the bolls of the trees are commonly distorted and 

 scarred owing to the battering which they receive when young by 

 driftwood and flotsam during times of high water. 



