486 BOTANICAL GAZETTE [JUNE 
to within a few centimeters of the surface, which is covered with a 
layer of dead but undecayed leaves. Two atmometers were 
maintained in woods of this type about 500 m. from the bunch- 
grass and blowouts. One of them was in a typical area of the 
vegetation (fig. 4), and the other in an area in which there were 
numerous young trees of Carya cordiformis. 
4.—Interior of Quercus velutina association, showing atmometer no. 7, July 
GATES. 
Fic 
1910; Sd by F 
The mixed forest association—In the mixed forest more than 
half of the trees are of species typical of the Quercus velutina asso- 
ciation which has preceded it. In this particular area, the oldest 
trees are without exception Quercus velutina, while near the edge 
there are some large Q. marilandica. There are also numerous 
young trees of Carya cordiformis, which are nearly as large as the 
more slowly growing oaks. ° Scattered among the individuals of 
these three species are a few trees of Gymnocladus dioica and Celtis 
occidentalis, the latter only near the margin. An actual count of 
