564 JOUENAL OF THE KOYAL HORTICULTURAL SOCIETY. 



higher plants, magnesium is most toxic and calcium least. There is an 

 antagonism between Ca and K, Mg and Na, and between K and Na, which 

 may be of some practical importance. For in the alkali lands, the harm- 

 ful effects may be due to the preponderance of one of these salts. 



The poisonous effects of Mg is, however, increased by the presence 

 of Ca, which is again the reverse of what happens with the higher plants. 



G. F. S.-E. 



Soil Bacteria, Influence of Depth of Cultivation on. By 



W. E. King, and 0. J. T. Doryland (U.S.A. Exp. Stn., Kansas, Bull. 

 161, August 1909). — The authors found that deep cultivation increased 

 the activity and numbers of bacteria in the soil. These were also 

 dependent to some extent upon moisture and especially upon temperature, 

 but appeared to vary also independently of these factors, possibly owing 

 to the production of by-products. The increase of activity was par- 

 ticularly shown in the amount of ammonia produced. An outline of the 

 methods employed is given. — F. J. C. 



Soils, Isolation of Harmful Organic Substances from. By 



0. Schreiner and E. C. Shorey (U.S.A. Exp. Stn., Bur. of Soils, Bull. 

 53 ; April 1909). — The authors have succeeded in isolating certain 

 crystalline organic substances from soils, of which picoline carboxylic 

 acid and dihydroxystearic acid are both shown to be harmful. Several 

 other crystalline organic substances were found, includiDg a new waxlike 

 body, agroceric acid, and a body belonging to the cholesterol group, 

 agrosterol. 



The isolation of these substances lends colour to the idea that 

 infertility may be due to the presence of certain inhibitory bodies of an 

 organic nature as previous investigations have suggested, and these 

 researches into and isolation of definite organic compounds from the 

 soil are important contributions to our knowledge of the causes of 

 infertility.—^ 7 . J. G. 



Soils, The Action of Heat and Antiseptics on. By S. U. 



Pickering (Journ. Agr. Sci., vol. ii. (1908), p. 32). — The author shows 

 that antiseptics, such as carbon bisulphide, chloroform, ether, benzene, 

 &C, cause chemical action to take place in soils treated with them and 

 increase the soluble organic matter in them. Germination is retarded, 

 just as in the case of heated soils. The different antiseptics differ in the 

 intensity of their action both as regards the amount of organic matter 

 rendered soluble and the inhibitory effect upon germination. After 

 keeping the soil for a time the inhibitory effect is reduced and some of 

 the previously soluble matter becomes insoluble. 



The production on heating of a substance inhibitory to germination 

 appears to be a property common to all soils, and the proportion of it 

 formed depends on the increase in the amount of organic matter rendered 

 soluble by heating, but the actual amount of soluble organic matter 

 originally present in the unheated soil is not always a criterion as to the 

 intensity of its inhibitory action. 



Soils in their natural condition appear to contain a certain amount of 

 this inhibitory substance, as they appear less favourable to germination 



