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 typeof 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. Theamount 
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. 
® Prunus serotina (Wild Black Cherry)....3 to 18 in. 
3 Platanus occidentalis (Sycamore)...... 12 to 24 in. 
® Juglans nigra (Black Walnut).......... 6 to 18 in. 
Die SE eae TA Ease SV es SEN) a's eh cva 510.6 « «a/c cece ae 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 
