Citrrent Literature. 99 



eases of small fruits are described in one section, those of vege- 

 table and field crops in another, cereals in another, trees and 

 timber in another and so on. 



Disorders due to physical or chemical agencies receive some 

 attention — though quite inadequate. But a wide range of 

 fungous diseases is dealt with. The illustrations are fair, and the 

 text clear. Many references to the literature are given in the 

 form of foot notes. On the whole, the book commends itself as a 

 useful reference work for students and especially for plant pro- 

 ducers. J. H. F. 



The Isolation of Harmful Organic Substances from Soils. By 

 Oswald Schreiner and Edmund C. Shorey. U. S. Department of 

 Agriculture, Bureau of Soils. Bulletin No. 53. 



The suggestion that the infertility of certain soils might be due 

 to organic substances injurious to plants was put forward by the 

 Bureau of Soils about five years ago. At that time experiments 

 showed that poisonous substances undoubtedly were present in 

 the soils, but just what they were was only a matter of conjecture. 

 The next step in the investigation was to determine the effect of 

 known decomposition products of plants, especially the decom- 

 position products of proteids and related substances, upon plants 

 grown in laboratory cultures. This was done on the assumption 

 that such substances or similar substances might be found in 

 exhausted soils. Of eighteen nitrogenous substances found in 

 living or decaying plant structures, twelve were poisonous, two 

 neutral and four beneficial to wheat cultures when applied in 

 concentrations varying from one-ten-thousandth to one-tenth of 

 one per cent. These and similar experiments were described in 

 Bulletin 47. 



During this time the investigators were continually trying 

 actually to isolate the harmful substances from- certain soils of 

 known infertility, and they were finally successful as described in 

 the Bulletin under review. They obtained four organic com- 

 pounds, dihydroxystearic acid, picoline carboxylic acid, agroceric 

 acid and agrosteral, all well defined crystalline bodies, one of 

 which is quite injurious, one slightly harmful but closely related 

 to much more harmful compounds and two that are not harmful, 

 so far as the wheat seedlings used in the tests are concerned. 



