SVLVICILTUEE. 



I. In primitive forests tlie species wliicli harmonize are those 

 whicli differ botanically. 



J. \^nien two species are so alike as to be almost varieties but 

 hiive, nevertheless, different climatic needs, then they are, in reality, 

 Inie and distinct species (Douglas Fir in Colorado and Oregon). 



K. Frcst injury is always due to the death of the plasmodium 

 killed l?y the direct action of the frost. The plasmodium is most 

 sensitive during the time of cell formation and of active groAvth. 

 The Plasmodium in the inert stage, as in seeds, is actually insensitive. 



L. All species become more hardy as they grow older. This is 

 simply due to the trees rising above the cold layers of temperature 

 near the ground and to the greater thickness and mass of the trunk, 

 resisting rapid changes of temjierature. 



M. The degree of moisture in the air required for forest growth 

 is 50% relative humidity during the growing season. The broad- 

 leaved trees and the two and three needled Pines are the species 

 best adapted to regions of extreme dryness or of sudden changes 

 in atmospheric moisture. 



X. The association of trees into a forest has the effect of increas- 

 ing the relative humidity by not to exceed 10%. Hence the neces-, 

 sity of maintaining forest in regions where the tension of watery 

 vapor is close to 50%. The partial destruction of a forest may 

 entail the death of the remainder rendering reforestation impossible 

 unless it is started from the nearest adjoining forest. Inside a 

 forest the greater atmospheric humidity acts as beneficially as a 

 moist ocean wind, lacking, however, the latter's violence. 



0. It is in moist, cool localities (mountains and northern cli- 

 mate) that climatic variations are the least extreme during the 

 growing season. It is here that the annual rings are equal, the 

 grain fine and regular, and the timber of the greatest commercial 

 utility. 



P. The moister the climate, the easier becomes forest culture, 

 and the forester is apt to make tlie least mistakes in thinnings, 

 regeneration, fellings, etc. Air moisture seems to exercise a favor- 

 able influence on the straightness of the stems. 



Q. It is known that a failure of rain for several days may be 

 fatal to young plants. The faculty of persistence increases ' with 

 age, and the grown trees can endure long periods of drought. If, 

 however, the lack of rain is such as to bring the sum total of 

 precipitations during the four months of the growing season below 

 the two-inch mark, then the forest disappears, even if the humidity 



