27 



plants are sometimes observed in frosty localities with every twig 

 tipped with a dead spring shoot. Cold snaps occurring in the spring- 

 shortly after growth has begun occasionally damage old and young 

 stock by killing back the tender shoots, and thus impede the year's 

 growth. Observations made in the Capitan Mountains, New Mexico, 

 indicate that Douglas fir is damaged less by late frost than limber, 

 j'^ellow, and pinon pines and white fir. 



In German plantations, where both forms are grown side by side, 

 the foliage of the coast fir is found to suffer considerabty from severe 

 winter temperatures, especially when the aspect is southerly. The 

 needles on the south sides of the plants turn bright red and drop off 

 the next spring. This weakness is entirely unknown in the moun- 

 tain form, wdiose needles are well protected by a waxy cuticle from 

 excessive winter transpiration. 



In European plantations the mountain form, coming from a cli- 

 mate characterized by seA^ere winters and dry summers, for a time 

 promised by virtue of its greater hardiness to supersede the coast 

 fir. This, however, it has failed to do, owing to the fact that, although 

 coast fir is less frost-hardy, it is not sufficiently so to prevent its growth 

 in many situations, or to counterbalance its superiority in the matter 

 of rapidity of growth. In the United States, cultural experiments 

 in the Northeast with the coast fir have hitherto yielded poor results, 

 because it has not been able to withstand the eastern climate. The 

 mountain fir, on the other hand, has in some localities made slow but 

 fairly persistent growth since its mtroduction in 18G3. 



In the northern Rocky Mountains Douglas fir is often damaged by 

 frost cracks, or " gum checks," which are longitudinal splits in the 

 trunks, caused by the unequal contraction of the inner and outer 

 parts of the stem under the influence of sudden and extreme cold. 

 Frost cracks usually become partially or wholly filled with pitch, 

 when they present an easy access for fire into the trunk and up to 

 the crown. They also open the way for insects and fungi, and trees 

 which show frost cracks should therefore be removed, if practicable, 

 whenever they are met with in timber marking. A " gum check " is a 

 bad defect in a log, especially if it is spiral. 



In the Kocky Mountains, Douglas fir seedlings frequently fall prey 

 to drought, which is a potent factor in restricting its lower altitudinal 

 range. 



Douglas fir is very easil}^ killed by sulphur fumes from smelters, 

 and is more susceptible to damage from this source than lodgepole 

 pine. In the vicinity of Anaconda, Mont., the radius of damage from 

 smelter fumes is from 10 to 12 miles. 



[Cir. 150] 



