Z0 BULLETIN 24, U. S. DEPARTMENT OF AGRICULTURE. 
MIXED HARDWOOD STANDS. 
Cottonwood grows in mixture either with willow or with other 
hardwoods. It is more often found with the hardwoods on the better 
drained glades and ridges throughout the bottom-land areas. The 
mixture differs in the north and south portions of the valley. The 
predominating species associating with cottonwood in the upper 
Mississippi Valley are silver maple, white elm, river birch, sycamore, 
boxelder, and ash. Other species are butternut, shellbark hickory, 
black walnut, pin oak, hackberry, and coffeetree. Most of these occur 
also through much of the lower valley region, especially sycamore, 
ash, hackberry, and boxelder. Several other species, however, which 
are abundant in the South, become scarce or entirely disappear from 
the composition as one proceeds north through the upper valley. 
This is true particularly of red gum, tupelo, cypress, pecan, willow 
oak, overcup oak, and cow oak. In addition to those already listed, 
the following trees of minor value are often found with cottonwood 
in “either or both parts of the valley: Honey locust, black locust, 
dogwood, mulberry, pawpaw, red elm, redbud, and hawthorn. Per- 
haps the most characteristic associates of cottonwood in the north- 
ern part of the valley are the silver maple and white elm, while 
sycamore, hackberry, and red gum occur most abundantly with it in 
the south. Nearly all of the associated species are present in the cen- 
tral sections of the valley, including extensive bottomland areas 
in Missouri, Arkansas, Illinois, Tennessee, and Kentucky. 
In certain parts of the bottoms, three classes of situations sup- 
porting forest growth may be recognized, namely, the “ glades,” 
the “ridges,” and the “back sloughs.” The sloughs remain under 
water during the larger part of the growing season and their charac- 
teristic forest growth is cypress and tupelo gum. Cottonwood prac- 
tically never grows there. The bottoms subject to overflow for from 
a few weeks to several months are sometimes spoken of collectively as 
the “ glades.” ‘These in ,turn\ may be irregularly divided by low 
“ridges,” which are seldom over 6 feet in elevation, and often slope 
almost imperceptibly to the level of the glades. The ridges and the 
glades, however, are often not clearly defined, and even where they 
are well marked the forest composition seems to be but little gov- 
erned by them. Sycamore, pecan, shellbark hickory, and boxelder 
are possibly more common on the better drained ridges. 
In mixed hardwood stands the cottonwood occurs in all propor- 
tions from only one to two trees per acre up to nearly a pure stand. 
Frequently cottonwood occurs in small groups on the lower depres- 
sions. Such groups may have 10, 20, or more trees. At times the 
cottonwood, either single trees or groups, seems to be restricted to 
higher elevations, apparently because at the time of seeding the 
