110 C. O. ROSENDAHL AND F. K. BUTTERS 



few larger individuals, some of them old and broken by the 

 wind, which attain diameters of 14 to 16 inches. 



In some of the largest trees cuts were made to a depth of 2^ to 

 3 inches and fifty to sixty yearly rings were counted. Granting 

 that the growth was much more rapid in the earlier periods of the 

 life of the trees it is safe to estimate that these individuals ranged 

 in age from ninety to over one hundred years. One old stump, 

 about 12 inches in diameter and probably cut some ten years 

 ago, showed over ninety rings. This clearly proves that the 

 grove is not a planted one for the neighboring country was first 

 settled by white men in the early fifties of the last century. 



That the grove is a natural one is further attested by the fact 

 that associated with the pines are a number of species of herbs 

 and shrubs which occur typically with the Jack pine in the north. 

 The most noteworthy of these are Oryzopsis pungens (Torr.) 

 Hitch., Carex siccata Dewey, and Vaccinium pennsylvanicum Lam. 

 The first two of these have not been found previously in Minne- 

 sota outside of the pine area. Other species found in the grove, 

 which grow most abundantly in northern Minnesota, are Chima- 

 phila umbellata (L.) Nutt., Hepatica americana (D.C.) Ker., 

 Houstonia longifolia Gaertn., and Lupinus perennis L. A num- 

 ber of the above named species occur abundantly with the Jack 

 pines in Wisconsin, 50 to 60 miles to the northeast, and appear to 

 be natural concomitants of the Jack pine forests of Minnesota 

 and Wisconsin. 



These facts all prove conclusively that the grove in the Root 

 River valley, lying 50 miles outside the present limits of con- 

 tinuous pine forests, is a patch of natural Jack pine forest which 

 has in some way become isolated and has succeeded in maintain- 

 ing its existence in all probability since glacial times. In at- 

 tempting to account for the presence of this grove in southeast- 

 ern Minnesota, together with the twenty-six to thirty scattered 

 occurrences of white pine, the most plausible explanation is that 

 they are all relics of a former general distribution of pine forests 

 throughout this area of the state. 



The southeastern part of the state now covered by deciduous 

 forest, or more correctly speaking, that which was so covered at 



