78 BIG SPRING PRAIRIE. 



about all of the trees upon the newly occupied area. 

 Upon most of this area between the depressions repre- 

 sented on Map II, numerous young trees of Populus 

 deltoides (Cottonwood) ; Populus tremuloides (Trem- 

 bling Aspen); and Ulmus americana (American Elm), 

 were gaining a foothold. 



One of the clay islands in the western part of the 

 prairie contains only Elms. The other clay islands or 

 clay banks represented exhibit slight variations in the 

 relative number of the species enumerated above, but 

 all of the species are characterized by the prominent or 

 exposed roots. 



Fig. 17 represents a peculiar formation of a Maple 

 tree which occurs a short distance southwest of one of 

 the clay islands in the western part of the prairie. The 

 clay-bed gradually sloped from the island in either 

 direction. After drainage a seedling maple sprang up 

 and flourished for several years. As the muck is^ 

 deeper here than on the island, the tips of the larger 

 roots only were imbedded in the clay; as a result the 

 tree could not successfully withstand the strong wind 

 to which it was exposed. When it was blown down, 

 the roots were not broken off as commonly happens, 

 when they are imbedded in hard soil. The roots on 

 the windward side were torn loose, and have decayed 

 as can be noted by a careful inspection of cut. 



Those on the side nearest the prostrate trunk were 

 but little disturbed. Hence the tree continued its 

 growth. The principal branches survived in their 

 struggle for existence, the other branches being shaded 

 gradually decayed, and the resulting formation ensued. 

 This is an apt illustration of a successful struggle for 

 existence under adverse conditions. The illustration 

 shows in the back-ground another tree not so suc- 

 cessful in its struggle. The mere looseness of soil on 

 prairie where muck is quite deep may be sufficient 

 reason to account in part for the absence of trees of any 

 size on such areas. 



