120 



SCIENCE 



[N. S. Vol. XLI. No. 1047 



phenomena can be understood and inter- 

 preted only in the light of sociological 

 knowledge. So also with forestry. For- 

 estry depends upon the anatomy and 

 physiology of plants, but it is not applied 

 anatomy and physiology of plants. With 

 foresters, anatomy and physiology of plants 

 is not the immediate end but enters only 

 as one of the essential parts without which 

 it is impossible to grasp the processes that 

 take place in the forest. As the science of 

 tree societies, forestry really is a part of 

 the larger science dealing with plant asso- 

 ciations, yet its development was entirely 

 independenjjf of botanical geography. 

 When the need arose for the rational 

 handling of timberlands, no science of plant 

 association was in existence. Forestets 

 were compelled to study the biology of the 

 forest by the best methods available; they 

 used the general scientific methods of in- 

 vestigation and developed their own meth- 

 ods when the former proved inadequate. 

 I am frank to admit that the present 

 knowledge of plant associations in botany 

 has not yet reached a point where foresters 

 could leave wholly to botanists the working 

 out of the basic facts about the life of the 

 forests which are needed in the practise of 

 forestry. When the general science of 

 plant associations has reached a higher 

 state of development, the two may possibly 

 merge, but not until then. 



In developing the science of tree asso-, 

 ciations, the forester has been unquestion- 

 ably favored by the fact that the forests, 

 being the highest expression of social plant 

 life, afford the best opportunity for ob- 

 serving it. 



The reason for the ability of forest trees 

 to form most highly organized plant soci- 

 eties lies in their mode of growth. Each 

 annual ring of growth, together with the 

 new leaves that appear every year, are in 

 reality new colonies of cells. Some of the 



cells die toward the end of the vegetative 

 season; others continue to live for a num- 

 ber of years. When the conditions of life 

 in a forest have changed for a certain tree ; 

 when, for instance, from a dominant tree 

 it became a suppressed one, the new col- 

 onies of cells formed during that year, and 

 which sustain the life of that tree, are natu- 

 rally adapted to these new conditions. 

 The same is true when a suppressed tree, 

 through some accident to its neighbors, 

 comes into full enjoyment of light. The 

 last annual growth is at once capable of 

 taking advantage of the new situation 

 created in the forest. Therefore, as long 

 as the tree can form annual rings, it pos- 

 sesses the elasticity and adaptability essen- 

 tial for trees living in dense stands. It is 

 only when a tree is suppressed to a point 

 when it can not form new growth that it 

 dies and is eliminated from a stand. Be- 

 cause of the fact that the forest is the 

 highest expression of social plant life, the 

 foresters occupy the strategic position from 

 which they command vistas accessible only 

 with difficulty to other naturalists. In 

 this lies the strength of forestry, its peculiar 

 beauty, and the debt which natural science 

 owes to it. It is a significant fact, although, 

 of course, only of historic importance, that, 

 according to Charles Darwin^ himself, it 

 was ' ' an obscure writer on forest trees who, 

 in 1830, in Scotland (that is, 29 years be- 

 fore the 'Origin of Species' was published), 

 most expressly and clearly anticipated his 

 views on natural selection in a book on 

 Naval Timber and Arboriculture." For 

 the same reason it was foresters, who, long 

 before the word "ecology" was coined, 

 have assembled a vast amount of material 

 on the life of the forest as a plant associa- 

 tion — the basis of their silvicultural prac- 

 tise. Warming, Sehimper, and other early 

 writers on ecology, borrowed most of their 



2 ' ' Origin of Speeies. ' ' 



