168 College of Forestry 
diate points between the extremes of water deficit and water 
surfeit. 
We have already pointed out (p. 26, that the fixed hab- 
itat relation or static character of the typical higher plant 
entailed the accumulation upon the ground it occupies of 
dead organic stuff, not merely the yearly fall of leaves, 
branches, fruits, ete., but the bodies of great trees and of 
generation after generation of whatever growth forms make 
up vegetation. Such accumulations constitute on the one 
hand a great supply of potential energy, but on the other a 
ereat menace that by their continued piling up they will 
make the site unhabitable. It seems to me that perhaps next 
to the wonderful photosynthetic power of plants, the manner 
in which this menace has been made a source of energy for 
further plant production is the most noteworthy. It looks 
as if the whole course of vegetation development as we have 
followed it tended toward the stage when this supply of 
potential energy should be made to yield actual productive 
energy, and that when this point is reached we have the pos- 
sibility of producing not only the maximum plant growth 
upon the land but also the support of the most highly differ- 
entiated plant society. In our climate the natural vegetation 
in which these conditions are realized is the climax forest. 
In cultivated vegetation the maximum crop yield is realized 
when, other things equal, the highest energy yield of the soil 
is maintained. As to what this energy is and how it may be 
freed, we are learning by experience and research, but cer- 
tainly a study of the behavior of native vegetation will also 
teach us. 
Characteristics of a Climax Forest Society. 
In a climax forest then, we have a number of environ- 
mental conditions and plant relations which may be best ap- 
preciated by stating them serially: 
(1) As to the soil: 
(a) It is mechanically affected by the penetration of the 
great roots of the dominating forest trees. 
(b) It is well drained and well aerated. 
