A STUDY OF THE ROOT-SYSTEMS OF PRAIRIE 



PLANTS OF SOUTHEASTERN WASHINGTON r f% "*>*« 



HERA 



University of Minnesota, Minneapolis, Minn. V"""^\. 



i. & m 



EAVE "^* j 





While carrying on a study of the plant formations and associ- 

 ations of semi-arid southeastern Washington in 1912-1914, it 

 soon became apparent that for a proper understanding of the 

 development and structure of these associations a knowledge 

 of the root-systems of the more important prairie species was 

 imperative. Consequently, during the fall, winter, and spring 

 of 1913-1914, more than 350 root-systems of 25 of the most 

 important ecological species were examined. This paper con- 

 tains descriptions of these, together with a discussion of the con- 

 ditions under which the plants grow. 



The prairies of southeastern Washington, and their eastward 

 extension into adjacent Idaho, occupy a position between the 

 foothills of the Bitterroot Mountains on the east, and the sage- 

 brush region of western Adams, eastern Franklin, and western 

 Walla Walla counties, Washington, on the west. On the south 

 they are bounded by that high upfold of the lava-rock known 

 as the Blue Mountains. Northward the Spokane gravels, ex- 

 tending somewhat southward of Spokane, with their open 

 growth of yellow pine, mark at once the general northern bound- 

 ary of the exposed part of the great lava sheet and its accompany- 

 ing prairie formation. As the great Columbian Plateau with its 

 wind-moulded hills ascends to an altitude of 2700 feet near its 

 eastern border, the precipitation correspondingly increases, and 

 this reflects itself in a more highly developed type of prairie 

 vegetation. In fact, the well-developed high prairies occupy 

 a relatively narrow belt of 30-50 miles in diameter along the 

 eastern edge of the plateau, while the area westward is char- 



THE PLANT WORLD, VOL. 18. NO. 9, 1915 



