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made during the five years which I spent in 

 this work in Germany, Austria, and France, and 

 data also gathered from the scientific papers of 

 Prof. Dr. Mayr ; and, finally, from the very 

 comprehensive reports on the results of planting 

 experiments in the State forests of Germany and 

 Austria and the private woods of Great Britain. 

 In order to spare as much detail as possible on 

 the subject as to the amount of warmth which 

 must be allowed to a given species of timber 

 during its period of vegetation in order to enable 

 it to begin and complete its growth in proper 

 time, the following way, which was originated by 

 Mayr, has been chosen. As all classes of timber 

 trees are connected with a certain climatic zone, 

 such trees may, inversely, be used for fixing the 

 climate, and the territorial distribution of a 

 particular species may be looked upon as a 

 climatic zone. Within this zone not only can 

 the typical species be grown, but also all other 

 kinds of trees found with it. Now, as the 

 classes of trees such as Abies, Picea, Larix, 

 Quercus, Fagus, Betula, &c., belong to the same 

 climatic zone all over the Northern Hemi- 

 sphere, it is quite enough, for delimitating the 

 climatic zone of any kind of timber, to mention 

 the typical species within whose territory it is 

 being or can be grown. The fact that some 

 particular kind of timber can be raised outside 



