24 



grade old trees and immature trees here form the forest. In the less 

 accessible areas back from the river many stands of virgin timber remain. 

 Finally, on accessible areas near the margin, even-aged stands of good 

 saw-log size indicate that early cutting was heavy in such places. Near 

 the channels and lower areas elm. soft maple, willow, honey locust, syca- 

 more, and ash are the commonest trees. Farther back, on the better 

 drained bottoms, pin oak often forms pure stands. The Kaskaskia for- 

 ests have a higher percentage of ash, hickory, and white oak than any 

 other bottomland forests of the state. They resemble those of the Big 

 Muddy and Wabash bottoms in the high percentage (42) of "hard- 

 woods", oak and hickory, which make up the stand ; but differ by the 

 absence of red and black gums, swamp Spanish and Schneck's caks. 

 Pecan is an occasional tree on the lower part of the river, extending up 

 as far as Carlyle. Samples, aggregating 6.12 acres, taken in three coun- 

 ties, show that the stands are largely made up of relatively few species 

 ( 12) in the following per cents : a.sh, 25 ; white oak, 14 ; soft maple, 13 ; 

 hickory, 13 ; elm, 11 ; pin oak, 11 ; black oak, 4 ; sycamore, 3 ; black wal- 

 nut, 3 ; hackberry, 2 ; river birch, honey locust, and cottonwood occasional. 

 Thus 91 per cent of the forest consists of hickory, ash, oak, elm, and 

 soft maple. 



These forests are being worked up chiefly as lumber. They contain 

 large amounts of low-grade species, such as pin oak, and lesser quantities 

 of merchantable ash, hickory, and walnut. 



A sample acre taken in virgin timber shows the following composi- 

 tion, yields, and sizes of individual trees which were characteristic of 

 forests growing on the moderately well-drained flood lands. 



The Mississippi River System 



Approximately one third the entire length of the Mississippi borders 

 Illinois. The difference in latitude between the extremes of the state is 

 more than five degrees. The mean annual temperature of the Cairo sta- 

 tion (58° F.) averages 10° F. warmer than that at the Dubuque, Iowa, 

 station (48° F.). The mean annual rainfall at Cairo (41.6 inches) aver- 

 ages 6.6 inches greater than that at Dubuque (35.0 inches). The effect 

 of these factors on the forest is to lessen the number of species in the 

 association, and to cut down the growth-rates of the northern as com- 

 pared with the southern forests. 



