24 BOOKS AND CURRENT LITERATURE 



The great variations in the amount of carbohydrates in plants 

 grown under different nutrient conditions, and in different parts of the 

 same plant, indicate that in studying problems concerned with plant 

 metabolism it is necessary to know the specific environment of the 

 plant as a whole, and of its several parts. 



Lack of fruit development is not alone due to the lack of pollination 

 or fertilization, nor are the greatest number of flowers produced by 

 conditions favoring highest vegetation or markedly suppressed vege- 

 tation. Pruning, as it effects the balancing of the carbohydrate 

 supply with the mositure and nitrogen supply will promote or retard 

 fruitfulness. — R. P. Hibbard. 



Height Growth of Young Conifers. — It has been a matter of 

 common observation with foresters that the height growth of young 

 conifers is more closely dependent on environmental conditions than 

 is the growth in diameter. Two papers have recently appeared de- 

 scribing efforts to determine which of the environmental conditions, 

 or what combination of them, is most important to vigorous height 

 growth. 



Brewster, 1 working at Priest River, Idaho, has compared the growth 

 of western larch (Larix occidentalis) for the years 1912-16, finding the 

 greatest growth in 1914, correlated with relatively high temperatures, 

 a maximum of sunny days and a generous, well distributed rainfall. 

 He attributes the best growth to the combined effect of these climatic 

 conditions. 



Pearson 2 has investigated the growth of western yellow pine (Pinus 

 ponderosa) in the very dissimilar climate near Flagstaff, Arizona. This 

 tree makes its greatest height growth during the months of lowest pre- 

 cipitation: April, May and June. When the growth depends solely 

 on the precipitation of earlier months it is very small ; when rains occur 

 in April and May the}' result in a marked increase of height growth. 

 The curves of relative humidity and number of cloudy days for the 

 years 1909-17 show a correlation with the curve of height growth which 

 is almost as close as that of the precipitation of April, May and June. 

 Temperature is regarded by the author as being most important in its 



Brewster, D. R. Relation between height growth of larch seedlings and 

 weather conditions. Jour. Forestry, 16: 861-870. Dec. 1918. 



2 Pearson, G. A. The relation between spring precipitation and height growth 

 of western yellow pine saplings in Arizona. Jour. Forestry, 16: 677-689. Oct. 

 1918. 



