28 Forestry Quarterly. 



pirically and unsystematically with more or less success. He has 

 discovered and applied his knowledge of the fact that different 

 species are not only more or less adaptive to varying soil condi- 

 tions but that their requirement for light is variable and that trees 

 as well as other plants can be divided into groups, according to 

 this relative requirement into light-needing and shade-enduring 

 ones, and finally this one factor of light influence for the devel- 

 opment of the crop has become so prominent, that one could de- 

 fine the art of the silviculturist, as the art of managing light con- 

 ditions in the growing forest so as to secure best results. Nor 

 is the forester satisfied to know the general broad features of the 

 biology of the species, their development from seed to maturity, 

 their requirements regarding soil, and light conditions, and their 

 general relations to surroundings ; but, as he is a producer of ma- 

 terials, he is most emphatically interested in the amount of pro- 

 duction and the rate at which this production takes place. For, 

 different from the agriculturist's crop, his is not an annual one, 

 but requires many years of accumulation, and as each year's wait- 

 ing increases the cost of production by tying up the capital in- 

 vested, it is of importance not only to know the likely progress of 

 the crop but also how its progress may be influenced. 



Here is a phase of biological dendrology, the mathematics of 

 accretion, which to most botanists is probably an unknown depth 

 and as far as our own species are concerned largely an unex- 

 plored area even. Foresters almost exclusively have developed 

 this portion of botanical science. The laws of accretion have 

 through many years of measurement, especially by German for- 

 esters, been recognized, and form a most fascinating study. As 

 in man's development the infantile, juvenile, adolescent, virile, 

 and senile stages are recognized, so in tree life these stages appear, 

 and the dependence of tree growth on its environment — "the fac- 

 tors of site" — is even more pronounced and readily recognizable 

 than in the animal, which can change its "site". 



Besides the more intimate knowledge of trees and tree life, 

 some knowledge of the lower vegetation especially in its ecologic 

 relations is of service. Weeds are enemies to be overcome ; but 

 they also are indicators of soil conditions and of light conditions, 

 and hence the study of what the Germans call Standortsgew'dchse 

 — plants indicative of the character of the site — forms a special 

 branch. Again fungi are destructive to the young crop and 



