10 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. 



Sealed cones as old as 75 and 80 years have been found attached to 

 the parent tree. Sometimes the lower part, or even the entire cone, 

 is embedded in the wood. Closed cones are more common on old 

 than on young trees, and on trees growing in dense stands than on 

 those in the open. MacDonald found on the Targhee Forest that 

 on trees less than 55 years old five-sixths of the cones opened at ma- 

 turity, while on trees over 55 years old only one-fourth of the cones 

 opened. Seeds retain their vitality for many years in sealed cones, 

 and in one case had a germination per cent as high as 8 after being 

 locked up for about 75 years. 



Clements states that cones open normally as a result of the drying 

 out of the cone scales rather than from the action of heat alone. The 

 majority of cones capable of opening normally probably do so within 

 a short time after maturity, and scatter their seeds while still attached 

 to the tree. Some cones, however, after remaining upon the tree 

 closed or only partly open for a number of years finally fall to the 

 ground with more or less seed still in them. 



There appear to be two distinct periods of general opening, the 

 first in the years immediately following maturity and the second from 

 10 to 13 years later. The opening during the second period is prob- 

 ably due to the fact that the pedicel of the cone breaks about this 

 time and the cone no longer receives moisture from the tree. The 

 size of the cone appears to have no effect upon the time when it opens. 



Tower 1 states that the amount of lime in the soil has a strong 

 influence upon the time when the cones open; that on soils rich in 

 silica and deficient in lime the majority of cones open at maturity, 

 while on soils rich in lime they remain closed and persist on the trees 

 for many years. Observations by other investigators in Colorado 

 and Montana, however, indicate that this tendency is not sufficiently 

 marked to constitute a rule. Individual trees in the same stand show 

 the most extreme differences in cone opening; one tree may have all 

 of its cones open, while beside it another tree of the same age may 

 have all of its cones closed; and in most cases both open and closed 

 cones are found on the same tree. Probably the differences in be- 

 havior in this respect observed by Tower indicate merely the general 

 tendency of cones to open less promptly on dry soils. This tendency 

 is also indicated by the fact that fewer cones remain closed on the 

 moister soils and in the moister climates of northwestern Montana, 

 northern Idaho, and the Sierras in California. 



The opening of the cone frees the small, winged seeds, which are 

 distributed mainly by the wind. Other agents of seed distribution 

 are gravity, surface drainage and streams, and such animals as 

 squirrels and mice. The distance to which wind distribution is effec- 



1 A Study of the Reproductive Characteristics of Lodgepole Pine, by G. E. Tower, in 

 Vol. IV, No. 1, of the Proceedings of the Society of American Foresters. 



