414 JOURNAL OF FORESTRY 



Our field tests have shown that, with the ideal soil, the relative 

 chances for lodgepole germination are 91 per cent in northern Colo- 

 rado, 49 per cent near the southern limit of the range in Colorado, and 

 about 57 per cent in the Pikes Peak region. This is the response of 

 the species to the varied climatic characters of these localities. Con- 

 sidering that under the best of these conditions probably not one seed 

 in a thousand is permitted to produce a tree, it is readily seen that in 

 the other localities an extremely slight barrier in the form of an inimical 

 soil, or a subnormal season, would completely prohibit lodgepole repro- 

 duction. From consideration of the climatic element at the outskirts 

 of the range, therefore, it appears highly probable that lodgepole has 

 already reached the limits of its rapid migration. Further migration 

 will doubtless result from the development of those qualities of vigor 

 in the seed which the central Colorado form has been shown to 

 possess in a slight degree. 



What now of that very peculiar condition in lodgepole which 

 causes it to retain so many of its cones, unopened, on the limbs, a 

 phenomenon which has the most important bearing on the reproduc- 

 tion of the species, especially after fires. Extracting tests give a 

 number of valuable facts. All collections of cones contain some which 

 will not open by air-drying. Of these, many are not influenced by 

 artificial drying at 110° F., but most of them open at 140° F., and 

 only a very few plainly defective cones resist a temperature of 170° 

 or 200°. In the siliceous form of lodgepole these resistant cones appear 

 to be of normal development, but are very heavy, and either contain 

 water in excess, or, as suggested by Clements,^ unusual quantities of 

 resin. The fact that in this form the number of such cones decreases 

 rapidly with continued air-drying, however, tends to controvert the 

 theory that the moisture is held in the cones by a heavy resin coating. 

 I^hese cones produce seed of normal germinability. In the limestone 

 form, resistant cones are generally under-developed, their number 

 increases if the cones are air-dried and become hard and fixed, and 

 the seed from them is of comparatively low germination. Perhaps 

 the most important point in this connection is obtained from a purely 

 physical consideration of the heat requirements of cones. . Opening of 

 fresh green cones is accomplished by the utilization of about as much 

 heat as would be required to vaporize an amount of free water equal 



9 Clements, Dr. F. E., "The Life History of Lodgepole Bum Forests." Bull. 

 79. U. S. F. S. 



