Wheeler: THE FLORA OF THE RED RIVER VALLEY. 699 



EXPLANATION OF PLATK XXXIV. 



General view of prairie near Shirley, Minn. This is the charac- 

 teristic aspect of mesophytic prairie in the Red River valley. The 

 shrubs are Salix humilis, for the most part. The herbs in the fore- 

 ground are Asters. The view shows a minor tension line in which 

 Junciis dudleyi\% an abundant plant. On the right a growth of Poly- 

 gonum intermixed with Andropogon is seen. The view gives an idea 

 of the variety of the prairie vegetation. 



PLATE XXXV. 



An island of Hordcum surrounded by a border zone of Salix inter- 

 mingled with Symphoricarpos and Solidago. Such circular patches of 

 squirrel-tail grass marking slight depressions in the prairie are not un- 

 common and often reach a considerable size, even covering several acres. 



PLATE XXXVI. 



Prairie near Gentilly, Minn. In the background is seen the shrubby 

 and scanty arboreal vegetation along the Red Lake river. In the 

 middle distance a minor tension line of Hordeum is apparent extending, 

 in this case, several miles along the river. In the foreground Nabalus 

 racemosus, a characteristic wand plant of the region, is seen forming 

 an almost circular patch in the general grass vegetation. 



PLATE XXXVII. 



Gopher mound with characteristic vegetation. These mounds made 

 by Geomys bursarius are abundant on the prairie throughout the dis- 

 trict. Somewhat more xerophytic plants inhabit them than are found 

 upon the level prairie where they occur. Upon this particular mound 

 hazel-brush, Artemisia, Bouteloua, Solidago rigida and other semi- 

 xerophytic or strongly xerophytic plants have secured a foothold. 



PLATE XXXVIII. 



A growth of silver-berry Eleagnus argentea. This plant is 

 abundant throughout the district studied, in dry declivities or on slopes 

 of the rolling prairie. It is also abundant in pastures along the Red 

 Lake river. 



PLATE XXXIX. 



View of the margin of a grass meadow in the poplar scrub near 

 Maple lake showing three stands of Salix lucida, a common plant of 

 the tension zone between the meadow and the scrub. 



PLATE XL. 



View of xerophilous vegetation on knolls along a coulee cut in the 

 raised beach of the extinct Lake Agassiz near Fertile, Minn. The 





