62 BULLETIN 275, U. S. DEPARTMENT OF AGRICULTURE. 



OUTLOOK. 



The weak point in the example (white fir) discussed in this paper 

 lies in the fact that the numerical basis of trees examined is insuffi- 

 cient. Besides, what may be true for one set of conditions may 

 prove wrong in another. Extensive additional studies on white fir 

 in different regions of its range have been carried out during 1913. 



What has been done for white fir must be done for the other species 

 as well. Investigations on incense cedar have yielded suggestive 

 results; others are to follow. But not before all important species, 

 from the lowest to the most valuable, have been studied carefully 

 with regard to their pathology Can we expect to definitely figure the 

 total-loss factor for any unit. To-day we are standing at the very 

 beginnuag. Each species has its specific fungi, either one (as in the 

 case of incense cedar) , or practically one (as hi the case of white fir) , 

 or several (as in the case of Douglas fir, sugar pine, and yellow pine) . 

 The relative importance of each of these fungi, their relation to 

 influencing factors, their prevalence throughout the range of their 

 hosts, and, finally, the establishment of the critical age and age of 

 decline from a pathological point of view, are still to be worked out. 

 To this we must add the study of all the other components of the 

 total-loss factor. 



The amount of work left to be done is enormous and will require 

 many years. Concentration on the inferior species will yield results 

 in a shorter time, enabling us to establish general rules to guide us in 

 the transition period without causing too much damage to the 

 interests of future generations. 



