May, 1920] SOIL SCIENCE 255 



TOXIC AGENTS 



1759. Ritzemv Bos, J. Bijdrage tot de kennis van de werking der bordeauxsche pap op 

 de aardappleplant. [A contribution to the knowledge of the action of Bordeaux mixture on the 

 potat plant.] Tijdschr. Plantenz. 25: 77-9-1. 1919.— See Bot. Abs1 . 3 Entry L654. 



MISCELLANEOUS 



1760. Alvarado, Salustio. La fina estructura de los vasos lefiosos. (Nota previa.) 

 [Minute structure of wood vessels.] Bol. R. Soc. Espafiola Hist. Nat. 19: 60-75. Fig. 1-7. 

 1919— See Bot. Absts. 3, Entry 1567. 



1761. Barss, H. P. Prune troubles of non-parasitic nature. Better Fruit 13*: 7-8, 21 

 Jan., 1919.— See Bot. Absts. 3, Entry 1625. 



1762. van der Lek, H. A. A. Ouer de z. g. "verwelkingsziekten," in het bijzonder die 

 welke door Verticillium alboatrum veroorzaakt worden. [Regarding the so-called wilt diseases 

 especially those caused by Verticillium alboatrum.] Tijdschr. Plantonz. 24: 205-219. PI. 4 

 fig. 1-8. 1918. Ibid. 25: 17-52. PI. 1-8, fig. 1-4. 1919— See Bot. Absts. 3, Entry 1666. 



SOIL SCIENCE 



J. J. Skinner, Editor 

 GENERAL 



1763. Beaumont, A. B. Studies in the reversibility of the colloidal condition of soils. 

 Cornell Univ. Agric. Exp. Sta. Mem. 21 : 480-524. 1919.— The author holds that soil colloid- 

 ality is dependent to a considerable degree upon circumstances and environment. The col- 

 loidal condition of a soil is constantly changing being especially susceptible to moisture vari- 

 ations. Wetting and drying in its effect upon colloidal conditions is therefore the particular 

 phase set forth in the present study. — In discussing the modern conceptions or reversibility 

 as related to colloidal materials the author agrees with Oswald that the change is not deter- 

 mined in the main by the nature of the colloid itself but by the conditions that produce coag- 

 ulation. The term reversibility as generally used, that is to indicate a change from the 

 colloidal to non-colloidal state and vice versa, is found too narrow from the soil standpoint 

 and is broadened to include the changes between the sol and gel states.— In reviewing the 

 literature as to the effects of wetting and drying on soils, the physical changes which are set 

 up seem in general to be correlated with increased fertility. Cohesion and plasticity for in- 

 stance are generally reversed and most authorities attribute the commonly observed changes 

 to alterations in the colloidality of the soil. — After an extended experimentation with methods 

 the author selected three for use: (1) a modified Mitscherlich water-vapor-method, (2) a 

 modification of Ashley's dye method and (3) the ordinary suspension procedure. The first 

 two were used most extensively, the degree of hygroscopicity and the amount of dye absorbed 

 being considered as relative measures of colloidal content. In general temperature varia- 

 tions below 10°C. did not noticeably affect water vapor absorption. Dyes were absorbed dif- 

 ferently by soils according to the chemical character of the dye and the colloids present in 

 the soil. — Hygroscopicity of soil was decreased by successive air-drying, oven-drying and 

 ignition. The passage from the moist to air-dry state produced a greater colloidal change 

 than from the air-dry to oven-dry condition. Ignition produced a marked effect although 

 the hygroscopic values of some ignited soils were very high. Alternate wetting and drying 

 had little effect upon surface soils after the first passage. Such action with subsoils was cumu- 

 lative. Long immersion in water raised the hygroscopicity of a soil low in organic matter 

 and lowered it in a soil rich thereof. Leaching seemed to increase the water vapor absorp- 

 tion of soils. — As the same general results were attained with the dye method of estimating 

 colloidal content, the author concludes that the drying of a soil especially from the moist to 



BOTANICAL ABSTRACTS, VOL. Ill, NO. 5 



