212 EXPERIMENT STATION RECOBD. 



that the nitrogen of the zeolite acted more slowly than that of more readily 

 soluble nitrogenous fertilizers which tend to increase the growth of straw at 

 the expense of grain. 



On the relation of plants to soils, I. Canavaei (Stas. Sper. Agr. Ital., Jf5 

 (1912), No. 10, pp. 725-752, figs. Jf). — This article deals with studies of the com- 

 pcsition of the parent rocks, bacteriological condition, soil solution and tempera- 

 ture, and natural and cultivated plant growth of certain soils occurring near the 

 agricultural institute of Perugia. 



The plant as an indicator of the relative density of soil solutions, T. L. 

 Lyon and J. A. Bizzell (Proc. Amer. /S'oc. Agron., Jtf (1912), pp. 35-Jf9, fig. 1). — 

 Series of water, sand, and soil cultures with wheat are reported. 



" In the water cultures ui?ed in these experiments for growing wheat seedlings 

 the dry matter produced per unit of transpiration increased with the density of 

 the solution except in the case of A'eiy dilute solutions. 



"Wheat seedlings growing in crushed quartz containing the same nutrient 

 solutions as those used in the water cultures produced the same relative quan- 

 tities of dry matter per unit of transpiration as did the water cultures. 



" The quantitative production of dry matter per unit of transpiration was, in 

 each case, greater in the quartz than in the water culture of corresponding 

 strength. This may possibly be accounted for by the absorptive properties of 

 the quartz particles. 



" In a series of wire basket tests, in which rock superphosi^hate, muriate of 

 potash, and nitrate of soda were added to the soil in different baskets singly 

 and in various combinations, the crops grown in the fertilizer-treated baskets 

 produced in every case a greater quantity of dry matter per unit of transpira- 

 tion than did the unfertilized soil, and up to a certain point an increase in the 

 quantities of fertilizers used produced the same result. 



" Taking the relation of dry matter to transpiration as an indication of the 

 density of the media from which the plant absorbs its mineral nutriment, the 

 addition of fertilizers to the soil used in the experiment increased in every case 

 the density of the solution with which the absorbing root surfaces came in con- 

 tact, and in most cases the density of the soil solution was augmented by an 

 increase in the quantity of fertilizers applied. 



"A comparison of the method described with the electrical resistance method 

 shows that they agree in indicating a greater density of the nutrient solution in 

 the soil to which fertilizers, single and combined, are added, but that in certain 

 cases, notably when acid phosphate is applied, they are not in entire agreement. 



" The density of the soil solutions, as measured by the Wheatstone bridge, is 

 probably not the same as the effective density of the solution from which the 

 plant draws its nutriment." 



The action of frost on soils, P. Eheenbeeg and G. von Romberg (Jour. 

 Landw., 61 (1913), No. 1, pp. 73-86) .—The general conclusion from the investi- 

 gations here reported is that in soils the colloids of which are but slightly 

 affected by frost the latter causes a finer division of the soil particles and thus 

 increases the hygroscopicity of the soil, an increase of from 2 to 8 per cent 

 being observed. On the other hand, in soils the colloids of which are appre- 

 ciably affected by frost there may be a reduction of hygroscopicity of as much 

 as 4 per cent. 



Sunlight, W. McGeoege (Hawaii Sta. Rpt. 1912, pp. 59-62, fig. J).— Observa- 

 tions were made in cooperation with the Philippine Bureau of Science on the 

 actinic power of the sun, using for this puri>ose a solution of oxalic acid in 

 the presence of uranium acetate. It was found that the actinic effect of the 

 sun was highest at the spring and fall equinoxes and lowest at the summer and 

 winter solstices. 



