600 MINNESOTA BOTANICAL STUDIES. 
brows of the knolls are occupied almost exclusively by an Artemisza 
formation in which three or four species are present, Artemista 
frigida being the most abundant. Scrub poplars, hazel and Quercus 
form a sparse ‘‘ gallery wood.” Onthe upland Gazllardia, 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 /tzbes, 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. 
