2o6 Forestry Quarterly. 



cept without critical revision all of Prof. Mayr's statements and 

 conclusions as undisputed laws. They are not laws yet, but 

 merely presentiments of such laws, merely the first outlines of 

 the future structure of scientific silviculture, which is bound to 

 grow up on the basis of a scientific study of the forest. Some of 

 his statements may not be based on a sufficiently solid founda- 

 tion, future work may and doubtless will bring in many correc- 

 tions and show the faultiness of some of his conclusions, yet the 

 idea itself which points such a fruitful path to silviculture will 

 never die. His investigations are those of a geographer, with 

 all the good and bad sides of the geographic method of investi- 

 gation. 



He studied the forests in Europe, in Asia, and in America. 

 In his travels he compared the climates and forests of different 

 countries and his conclusions are the result of these comparative 

 geographical studies. Such geographical studies, while they are 

 extremely valuable, yet are not devoid of some subjective ele- 

 ment. These defects of personal observations over large fields 

 can be corrected only by means of intensive experimental meth- 

 ods of investigation over small areas. 



The book consists of three large parts, each subdivided into a 

 number of chapters: (i) Fundamental, Natural Laws of Silvi- 

 culture; (2) The Reproduction of the Forest; (3) The Growing 

 and Care of the Forest. Of these three parts the first one if of 

 the greatest importance to us, since the conclusions drawn there 

 are based on many facts observed by him in North America, 

 and for this reason is helpful in understanding our own forest 

 conditions as well as those of the entire world ; the other two 

 parts are more specific and their application is narrowed down 

 chiefly to European conditions. 



Mayr established both for the old and the new world a series 

 of forest regions. The basis for this division into forest regions 

 is the climate, which determines, not only the distribution of the 

 forest but its very existence. Of the climatic factors tempera- 

 ture and humidity of the air play the most important part. The 

 author considers the average temperature for the four vegetative 

 months as the one which determines the distribution of the 

 different species and the limit of forest extension. For the 

 northern hemisphere, the vegetative period occurs during the 

 "tetrahore," the months of May, June, July and August. For the 



