Journal of Agricultural Research 
Vol. XXV, No. i 
grain can be increased by adding nitrates to the soil at a late stage of 
growth. He attributes the characteristically low protein content of 
wheat of the Pacific Coast States to deficiency of soil nitrates rather 
than to purely climatic influences. Finally, Lipman and Waynick (20) 
have described rather profound effects of climate upon biological and 
chemical properties of the soil. 
Recent investigations in this field have included attempts either to 
analyze climatic conditions more closely in relation to growth out of 
doors, or to control some of the climatic factors within greenhouses. 
Thus, Briggs, Kidd, and West (4) analyzing the data of Kreusler for the 
growth of maize, found the increase of weight per unit of leaf area better 
correlated with variations of atmospheric temperature than with varia¬ 
tions of either illumination or rainfall. Their methods of treatment have 
been unfavorably criticised, however, by Fisher (5). In the case of peas 
grown in water cultures Brenchley (3) found the percentage rate of 
increase of the dry matter correlated with the temperature of the green¬ 
house at the foreperiod of growth, but with both temperature and sun¬ 
shine thereafter. Walster (40) conducted sand cultures of barley in 
greenhouses controlled approximately to 15 0 and 20° C., but with the 
atmospheric humidity subject to influence by temperature changes. 
With a liberal supply of nitrates provided in the nutrient salts the plants 
grown at the higher temperature were excessively vegetative, while the 
other cultures supported normal culm formation. Under these condi¬ 
tions the leaves of the plants grown at the higher temperature were com¬ 
paratively rich in soluble nitrogenous compounds, while they were rela¬ 
tively poor in sugars and other soluble carbohydrates. The reverse of 
this relation obtained with plants grown at the lower temperature. 
Differences were found in the distribution of various forms of phosphorus 
compounds in the plant tissue of the two types of cultures. The greatest 
quantitative difference found by chemical analysis, however, related to 
the polysaccharids. There were nearly 3 per cent more of these in the 
dry matter of the plants grown at 15 0 than in that produced at 20°. 
The foregoing abstracts may serve to indicate the relative importance 
of temperature differences in climatic effects upon plant growth, as well 
as the apparently specific compositional response of the plant thereto. 
It can be readily appreciated that such responses may bear important 
relations to disease resistance in the organism. As a matter of fact, 
plant pathologists have been giving increasing attention to environmental 
factors (12, ij y 14 , 29, 39) in the investigation of disease relations. 
Furthermore, the work of Kraus and Kraybill (16) indicates important 
relations to fruitfulness of the ratio between nitrogen and carbohydrates 
of plant tissues. The possible practical importance of climatic modifica¬ 
tions of plant composition thus becomes apparent. 
EXPERIMENTATION 
The more significant of the experiments to be described here were 
conducted in chambers especially constructed for regulation of atmos¬ 
pheric temperature and humidity. 3 Pending the development of these 
chambers the following preliminary test was made in greenhouses regu¬ 
lated roughly within different temperature ranges. 
3 Chambers for a similar purpose have been previously developed by Hottes, as mentioned by Peltier 
( 2q, p. 448 ); later developments have been described by Johnson (12). 
