12 



EMORY OAK IN SOUTHERN ARIZONA. 



, The mistletoe (PJioradendron flavescens (Pursh.) Nutt.) frequently 

 attacks the Emory oak, evidently gaming entrance in the younger 

 portions of the twigs. The clusters of mistletoe rob the limbs 

 attacked of a portion of their nutrition, often causing the outer portion 

 to dwindle and die. Severe attacks stunt the trees, and may in 

 extreme cases kill them. 



OTHER INJURIES. 



Occasional terrific hailstorms of a local character defoliate whole 

 stands, break tender shoots, and even scar the branches. A few trees 

 are girdled and killed by lightning. 



UTILIZATION. 



While there has been a limited utilization of Emory oak for poles, 

 posts, and mine timbers, it is used almost exclusively for fuel, for 

 which it is preferred to the other woods of the region. Where Emory 

 oak sells at $5 a cord for domestic firewood, the other oaks sell at 

 from $3.50 to $4. At the mines the usual price for Emory oak is 

 $3, and there is not a ready sale for the other oaks at $2. It is 

 commonly reputed to make a hotter fire and to leave less ash; yet 

 the comparative showing of Arizona white oak, under a careful test, 

 indicates that there is no warrant for the existing strong prejudice 

 against it. The results of this test are given in Table 3. 



TABLE 3. Comparison of the heating values of Emory oak and Arizona white oak. 1 



Determined by II. S. Belts, Forest Service. 



British thermal units. 



Table 3 shows that the heat value of an average sample, including 

 heartwood, sapwood, and bark, from a butt cut, is about 10 per 

 cent less in Arizona white oak than in Emory oak. The greatest 

 difference is in the bark, Emory oak being 28 per cent better than 

 the white oak. Since there is confusion in the popular mind be- 

 tween white oak and blue oak, which is admittedly inferior as a fuel, 

 this may be an explanation of a part of the prejudice; but men 



