BOOKp; AND CURRENT LITERATURE 301 



import ;iiit j)l;iiit typos and of relating quantitatively the growth and 

 behavior of these plants with various physical conditions of their 

 environment. The plants employed were Canadian field pea {Pisum 

 arvense), wheat (Triticum durum) and mountain brome grass {Bromus 

 marginatus) . These investigations were carried out in the years 1913 

 to 191G at three stations located on the Wasatch Mountains near the 

 Great Basin Forest Experiment Station. Three plant associations, 

 oak-])rush, aspen-fir and spruce-fir, were represented at elevations of 

 7100, 8700 and 10,000 feet respectively. Meteorological data were 

 recorded, summarized and related to growth, water requirement and 

 certain physiological functions of the plants studied. The plants were 

 grown in sealed cans. 



Some of the main characteristics of the three type zones were that 

 the mean annual temperature increased from the highest to the lowest 

 station, normal annual precipitation was greatest in the aspen-fir 

 association and evaporation during the growing season was greatest 

 at the oak-brush station. Evaporation was almost as great at the 

 spruce-fir station because of high wind velocity there. The duration 

 and intensity of sunshine were practically the same and barometiic 

 pressures were nearly constant for each station, though of course 

 cUffering in actual amounts due to differences in elevations. 



lit was found that the plants matured more rapidly as the efficienc}' 

 of the heat units increased. In the three associations studied, wheat 

 and peas reached full maturity only at the lowest station. Water 

 requirement determinations were in good relative agreement with 

 rates of evaporation, each being greatest in the oak-brush and least in 

 the aspen-fir association. The total length of leaves and the total 

 amount of dry weight produced were greatest in the aspen-fir asso- 

 ciation. The rates of these two plant processes varied inversely with 

 the evaporation rates. Stem elongation was greatest at the oak- 

 brush station and least at the aspen-fir station. There seemed to be 

 a direct relation between this plant process and temperature, while 

 apparently evaporation had little influence. Dry weight per unit leaf 

 area, however, seemed to vary inversely with the evaporation. — 

 Earl S. Johnston. 



