COTTONWOOD IN THE MISSISSIPPI VALLEY. Dal 
lower land was under water. This indirect influence of topography 
accounts for much of the variation in the character of occurrence of 
cottonwood in this mixed stand. 
If the cottonwood is well represented in such a mixed stand, there 
is often almost the appearance of a well-defined two-storied forest, 
in which the more shade-enduring species, such as elm, sycamore, ash, 
hackberry, or oak, are partially overtopped by the much faster 
growing cottonwood. By the fortieth or fiftieth year, however, the 
stand has usually opened enough to give the associate species room 
for growth. During the next 50 years these gradually fill in the 
space left vacant by the death of the cottonwoods. At the age of 
100 years such stands may contain less than half a dozen large cot- 
tonwoods to the acre. 
A pure stand of cottonwoods develops in a similar manner into a 
mixed stand as the trees reach maturity. In fact, during the 
early life of the pure cottonwood stands there is often an under- 
story of small sycamore, ash, elm, maple, and other species, which 
upon examination will generally show the same age as the cotton- 
woods. These associates, gradually augmented by others that come 
in as cottonwoods die, ultimately occupy the ground to the exclusion 
of the latter. 
COTTONWOOD-WILLOW STANDS. 
In the Mississippi Valley cottonwood is frequently associated with 
various willows, which compete with it in occupying newly made 
lands and bars. Black willow (Salita negra Marsh.) is the principal 
associate in the lower valley, while in the north the almondleaf or — 
peachleaf willow (Salta amygdaloides Anderss.) appears to be more 
common. ‘The latter, together with the small longleaf or sandbar 
willow (Salia fluviatilis Nutt.), which is common throughout 
the whole region, seems to appropriate nearly all the available 
cpen areas along the upper river, affording very little chance 
for the reproduction of cottonwood, which apparently seeds some- 
what later. Cottonwood-willow stands, therefore, are infrequent 
in the north and usually contain a very small proportion of cotton- 
wood. They are, however, comparatively common in the lower val- 
ley. Here the black willow and cottonwood seem to grow on more 
even terms, and both species make almost equally rapid growth for 
the first 20 to 25 years. The cottonwood, however, continues to 
develop, and on many situations may ultimately crowd the willow 
out of the stand. Since, however, the latter seems to be better adapted 
to poorly drained land, it is not uncommon to find it crowding out 
the cottonwood on wet, mucky soils. The cottonwood-willow stands 
are therefore of a very temporary character, few being over 30 years 
