258 Forestry Quarterly. 



the wood is not very satisfactory. "The woods in which tyloses 

 are abundant as a rule are durable," yet there is nothing to prove 

 that the presence of the tyloses is in any way responsible for the 

 increase in durability. It is shown that tyloses when strongly de- 

 veloped in the vessels of wood tend to keep air and liquids out of 

 the vessels, but in the case of impregnation of the wood with 

 creosote they apparently have no effect on the penetrability of the 

 other wood elements. 



This paper may well be considered a valuable contribution to 

 the knowledge of the subject, but more so because of the ques- 

 tions it raises than those it settles. Much remains to be learned 

 regarding the "practical significance" of tyloses. The plates are 

 excellent and demonstrate the great possibilities of photomicro- 

 graphy in the study of wood structure. S. J. R. 



A Meteorological Study of Parks and Timbered Areas in the 

 Western Yellow-Pine Forests of Arizona and New Mexico. By 

 G. A. Pearson. Reprint from Monthly Weather Review. Wash- 

 ington D. C. Vol. 41, 1914. Pp. 1615-1629. 



The object of the study was to determine the influence of the 

 forest cover upon climate locally in the Southwest, in so far as 

 this influence might be of importance in the management of 

 timberlands and the possible afforestation of parks and denuded 

 areas. Comparatively little attention was devoted to purely me- 

 teorological problems or to the influence of the forest upon the 

 general climate of the region. 



It was found that the mean annual temperature in the forest 

 is 2.7° F. higher than in the park, and the maximum averages 

 0.9° F. lower and the minimum 6.4" F. higher. The mean daily 

 range is y.^'^ F. smaller in the forest. This relation is believed to 

 be due to the influence of the forest canopy, partly by the action of 

 the tree crowns in checking the loss of heat by radiation, but 

 mainly by the deflection of cold air currents from surrounding 

 mountains and high mesas. The temperature of the soil in the 

 forest during the summer, when shaded by the trees was found 

 to be about 5° F. lower at a depth of two feet than at the same 

 depth in the park. 



The snowfall in the park is more even and the depth some- 

 what greater than in the forest where the crowns of the trees in- 



