THE BIOLOGICAL BASIS OF FORESTRY. 211 



living, working, energy-accumulating plant itself, whose growth 

 we set ourselves to understand. 



The tree may be studied from various points of view, but 

 the one most useful and most fundamental to all who are 

 concerned with the rearing of plants is the physiological — the 

 understanding of life processes. Nor must we confine our 

 attention to a laboratory study of the plant, but seek knowledge 

 and instruction in nature's laboratory, where for thousands of 

 years experiments have been in progress, where the secrets of 

 her laws and dispositions are to be obtained. In the forest 

 there are records of past struggles, past triumphs, and present 

 tendencies can we but read and interpret the face of nature. 

 Our first duty is to know the plant, to be thoroughly familiar 

 with its structure and its functions. 



With this object in view we cannot study the tree apart from 

 the soil in which its roots are fixed, from the atmosphere which 

 envelops its aerial organs, nor consider it away from its neigh- 

 bours. Each of these media contains factors which influence 

 the life and growth of the tree. The numerous factors present 

 in soil and air provide innumerable complexes of conditions for 

 the growth of the plant — these individual factors varying within 

 a certain range allowing of the tree's continued growth, but 

 outside the limits imposing a check or impairing the vitality 

 of the individual. Our business is to find out the exact 

 complex of factors, which when supplied to the tree induce 

 the maximum increment compatible with maximum vitality. 



The three cognate applied sciences, agriculture, horticulture, 

 and forestry have the same fundamental principles, and their 

 respective devotees should aim at supplying the objects of 

 their attention with optimum conditions for growth and 

 development. To do this the farmer and gardener can control 

 the media in which their plants live to a much greater extent 

 than can the forester. Does not the gardener, for instance, 

 besides controlling to a very great extent the factors of the soil, 

 in some cases control the atmospheric medium also ? Do not 

 the farmer and gardener also control the living environment 

 by the timely removal of undesirable species ? Have they not 

 also a quick return for their labour and capital by the cultiva- 

 tion of annual and biennial plants ? Now the value of the forest 

 crop is different, and the return on the initial expenditure is 

 long delayed. It behoves the forester, therefore, to reduce the 



