Development of Natural History. 131 



As in the previous period the mathematical subjects, 

 namely, forest measurement and forest valuation, were 

 more systematically developed than the natural history 

 basis of forestry practice; the slower progress of the 

 latter being caused by the greater difiSculties of studying 

 natural history and of utilizing direct observation. 



In botanical direction descriptive forest botany was 

 first developed and several good books were published by 

 Walther, Borhhausen, Bechstem, Reum, the latter 

 (1814), of high value, and also by BeTilen, Gwinner and 

 Eariig. 



In the direction of plant physiology Cotta early and 

 creditably attempted (1806) to explain the movement 

 and function of sap, but remained unnoticed. Mayer's 

 (1805-1808) essay on the influence of the natural forces 

 on the growth and nutrition of trees, contains interest- 

 ing physiological explanations for advanced silvicultural 

 practice. But these sporadic attempts to secure a bio- 

 logical basis were soon forgotten. Not until Theodor 

 Hartig (1878) published his Anatomy and Physiology 

 of Woody Plants was the necessity for exact investi- 

 gation of forest biology as a basis for silvicultural 

 practice fully recognized. With the development of 

 general biological botany or ecology a new era for silvi- 

 culture seems to have arrived. Perhaps in this connec- 

 tion there should be mentioned as one of the earlier im- 

 portant contributions of much moment, 0. Beyer's 

 Verhalten der Bdume gegen Licht und Schatten (1856) 

 ia which the theory of influence of light and shade on 

 forest development was elaborated. 



Among those who placed the study of pathology of 

 forest trees on a scientifle basis should be mentioned first 

 Willkomm ilSIQ), followed by B. Hartig. 



