THE IXFLUKXCE OF THIXXIXG 29 



very open. The difference in the original densities of the two stands 

 no doubt brings these comparison figures nearer each other, but it is 

 not beheved that this difference could be entirely responsible for the 

 great variance in number of live sporophores and in number of sporo- 

 phore-bearing trees exhibited by the data for the two areas. 



THE IXFLUEXCE OF THIXXIXG OX GRAND FIR INFECTED WITH 

 ECHIXODOXTIUM TIXCTORIUM 



The similarity of the general trend of the two curves (fig. i) is very 

 pronounced, indicating a simultaneous, although not equal, effect pro- 

 duced by the opening up of the stand. In order to ascertain whether 

 the rainfall of the region for the various years had a marked effect in 

 the variations shown by the two curves, a graph was platted, usii.g the 

 U. S. Weather Bureau reports as the source of the data. Xo direct 

 correlation could be traced between the three, the periods of greatest 

 annual precipitation often coinciding with or preceding the low vigor 

 points in the curves and vice versa. Kirkwood^ has shown that in trees 

 growing upon areas where the effect of precipitation is most apparent 

 in the seasonal growth of the tree a direct relation can be traced be- 

 tween the year of drought and the following season's growth. No 

 doubt in very moist situations such a reaction would not be possible. 



The influence of thinning on grand fir is quite similar to that pro- 

 duced in hemlock, although to a lesser extent. The comparison data 

 given in Table 2 show clearly the larger size measurements of the trees 

 in the cut-over area as compared to the uncut area, the most pronounced 

 contrast being evident in the sizes of the original crowns and the pres- 

 ence, in the case of the trees in the cut-over areas, of the secondary 

 crowns. A few words should be said here in reference to these unusual 

 productions of secondary branches. Tolerant tree species show a 

 greater and more rapid response to increased light in the matter of 

 crown expansion and in the development of adventitious shoots from 

 the older parts of the tree than intolerant species. The presence of 

 dormant buds on the older parts of the trees, lasting over for many 

 years from the time of their origin, is a characteristic of grand fir. 

 Very frequently these dormant buds are congregated in one place from 

 I to 4 feet from the ground and form raised burrs, or burls, on the 

 trunk. The axis of these buds extends usually in very regular, finely 

 radiating lines from the point of origin in the pith to the outer surface, 



^ Kirkwood. J. E. : The Influence of Preceding Seasons on the Growth of 

 Yellow Pine. 1914. In Torreya, v. 14, no. 7, pp. 115-125. 



