992 jouRNAi; 01' roRp:sTKY 



It was found that the herbs and shrubs of the forest floor are rela- 

 tively shallow-rooted, lying for the most part in the upper 18 inches of 

 soil. Here as in the prairie environment the water content of the soil 

 offers the logical explanation for the disposition of the root systems. It 

 is to be regretted that the author was unable to examine the root sys- 

 tems of forest dominants. The only parts of the root systems of the 

 trees examined were those lying in the upper eight inches of soil and 

 the depth of root penetration was undetermined. In the reviewer's 

 opinion, this is a fertile field for research, and it is hoped it can become 

 at least a part of the work of one or more of the forest research 

 stations. 



In this forest community the sub-stratum furnishes an excellent 

 medium with a high-water holding capacity to catch the precipitation of 

 winter as well as that of the frequent summer showers. The shade of 

 the dominants reduces the evaporating power of the air, while water 

 loss from the soil is retarded by the layer of duff. Studies on the 

 disposition of soil moisture showed that the greatest amount of avail- 

 able water during the growing season from June 10 to August 19, 

 1918, was in the upper 18 inches of soil. The layers from two to three 

 feet below the surface were found considerably dryer. The reviewer 

 ventures the opinion that the large demand on soil water at depths 

 below 18 inches by the tree dominants is an important factor in causing 

 the surface layers of the soil to hold more available water during the 

 growing season than layers at a depth of two or three feet. 



If the overwood were removed it is very likely the deeper layers 

 would contain more available water during the growing season than the 

 surface layers. 



A number of species were encountered and excavated in two or more 

 of the communities. Of the ten polydemic species described, each 

 growing in at least two different habitats, seven showed very marked 

 changes in their root habits, while two made practically no change, 

 and one exhibited but slight change. In this connection it might be 

 noted that the reviewer in his study of the initial root habit of more 

 than one hundred and fifty woody species found that the root habit of 

 certain species were much more amenable to change under change in 

 habitat than were others. Thus the hickories produced the same form 

 of initial root under various soil conditions, while the red maple, on 

 the other hand, varies its root habit with the slightest change in soil 

 conditions. 



