BIG SPRING PRAIRIE. 83 



seeds find such ready lodgment upon this bare soil, and 

 the conditions seem to be suitable for their germina- 

 tion, especially upon the banks sloping to the south. 

 Here there is a proper amount of light and heat in 

 connection with the ever-present moisture in this muck 

 soil. Along some few of the ditches, willows are the 

 predominent trees or shrubs. Maples occur only occa- 

 sionally. 



Most of the trees figured on Map II, originated 

 along ditches, and an inspection will show that elms 

 and poplars are the abundant species. 



On the Peter Brayton farm in Big Spring Town- 

 ship, Seneca County, there occurs a peculiar group of 

 trees along one of the ditches. This group comprises 

 several maples ranging from 18 inches to 30 inches in 

 diameter, a few elms, a couple of oaks, a black haw, an 

 ash, a dogwood, and several willows of 14 to 15 inches 

 in diameter, 



TREES ON BURNED AREAS. 



Prairie fires have been frequently assigned as the 

 cause of prairies and the absence of trees upon them; but 

 on Big Spring Prairie, fires are the direct cause of the 

 encroachment of thickets and forests upon it. If a 

 prairie fire burns simply the tops of the dead grasses, but 

 does not distroy the sod and roots, ordinary weeds make 

 but little headway in gaining foothold. Schimper 

 gives, as the cause of the density of sod, the fact that 

 grasses propagate abuntly by vegetative reproduc- 

 tion, and adds that this very density of grass rootstocks 

 and roots with their great capacity for the absorption 

 of soil moisture is one of the chief hindrances to the 

 germination of the seeds of trees and to the flourishing 

 of tree seedlings. Herbaceous plants, not including 

 grasses, can not engage in contest against woody plants. 



On an area on which sod and soil are burned, 

 mosses and a few annual herbs make their appearance 



