EXPERIMENT STATION BULLETINS. 657 



siderable. The result is that the temperature of the former is raised 

 above that of the latter. 



In humid regions the effect of density of the soil solution upon the 

 diminulion of evaporation and hence upon the rising of temperature, is 

 probably not very large but in the air dry regions — in the alkaline lands 

 — it must be verj^ considerable. 



The interesting question that arises now is, is the temperature of the 

 leaves of plants grown in different densities of solution any different. 

 The writer^'' has shown that the density of the plant cell sap increased 

 with the increase in concentration of the solution in which the plants 

 grew and that the relative transpiration or the number of grams of 

 water transpired to produce one gram of dry matter decreased, above 

 a certain point, with the increase in concentration of the solution. In 

 the light of all these facts the conclusion is irresistable that the leaves 

 of plants grown, in solutions of high concentration must have a higher 

 temperature during the summer than the leaves of plants grown in solu- 

 tion of low concentration. In the winter however, the former leaves 

 will have a. lower freezing point than the latter leaves. 



LOWERING OF TEMPERATURE. 



The effect of salt solutions upon the cooling or lowering of tempera- 

 ture of soils was studied in the same manner as the foregoing with few 

 exceptions. The chief differences being that the present study was con- 

 ducted in winter when the air temperature was very low, the thermom- 

 eters used were differently constructed, and that in some cases earthen- 

 ware jars 3 inches high and 3 inches in diameter were used instead of 

 the wooden boxes. The extent and nature of the work will be revealed 

 in the description and discussion of the following experiments: 



Experiment 1. This experiment consisted in studying the effect of 

 different concentrations of KCl and NH^Cl upon the rate of cooling and 

 the degree of lowering of the freezing point and also upon the rate of 

 thawing and rising of temperature. The experiment was prepared by 

 placing 1546 grams of quartz sand in the earthenware jars and adding 

 to the sand 300 cc of solutions of 0.0, 0.5, 1.0 and 1.5 normal of KCl 

 and NH^Cl ; then placing the vessels containing the sand outdoors upon 

 a stand during a cold night and taking records of the rate of falling of 

 temperature every 10 minutes with thermometers graduated to 0.2° F., 

 until the temperature of the sand in all the pots was about the same 

 as the air temperature. The next morning when the air temperature 

 began to rise, the jars were brought into the laboratory, whose tempera- 

 ture remained quite constant along 65° F., and the rate of thawing 

 and rising of temperature was studied by taking records every 10 min- 

 utes until the sand in all the different pots was about the same and 

 close to the room temperature. The data obtained in this experiment are 

 shown in the tables below with their accompanied charts: 



1* Bouyoucos, G. J. Transpiration of wheat seedlings as affected by different densities of a com- 

 plete nutrient solution in water, sand and soil cultures. 

 Beihefte zum Botanischen Ceutralblatt. 

 Heft 1. November, 1912. 



83 



