BIG SPRING PRAIRIE. 81 



APPEARANCE OF TREES ALONG DITCHES. 



It is a well known fact that trees and shrubs com- 

 monly occur along ditches or water courses even in the 

 west. Whenever drainage ditches are dug upon the 

 eastern type of prairie, a variable number of trees make 

 their appearance along their banks; the number and 

 kind of trees depending upon kind and quantity of 

 seeds finding lodgment upon the bare soil. The amount 

 of seeds received will depend upon proximity to source 

 of supply, and the direction of the prevailing winds at 

 the time of seed-dispersal. 



On Big Spring Prairie, those ditches occurring near 

 forests, (especially if the forests are so situated that the 

 prevailing winds can be instrumental in wafting the 

 seeds to the bare soil along them) are apt to exhibit a 

 greater number of species, and also a greater number of 

 individuals of each species, than those ditches not so 

 favorably situated. 



Fig. 18 represents a row of trees which sprang up 

 after the digging of the Brown Ditch. This row of 

 trees occurs partly on the western bank of ditch, and 

 partly on the eastern bank as indicated on Map II. 



This row of trees consists of 



DIAMETER 

 79 Ulmus americana (American Elm) 6 to 30 in. 



5 Prunus serotina (Wild Black Cherry). . ..3 to 18 in. 



3 Platanus occidentals (Sycamore) 12 to 24 in. 



3 Juglans nigra (Black Walnut) 6 to 18 in. 



2 Fraxinus sp ? (Ash) 10 to 12 in. 



The trees occur along the very margin of ditch. 

 The roots on the ditch side are considerably exposed 

 on account of erosion, occasioned by the deepening of 

 the outlet of ditch. From the foregoing list, it is evi- 

 dent that the elms are by far the most abundant species. 

 This is true of nearly all the other ditches. On the 

 very slopes of the ditches along new road No, 1, num- 

 erous cottonwoods and willows are springing up, as the 



