No. 1, October, 1920] TAXONOMY OF VASCULAR PLANTS 43 



of corn with rock phosphate but decreased it with acid phosphate. Leaching with a nutrient 

 solution containing ammonium nitrate as the source of nitrogen increased the availability of 

 the rock phosphate as measured by the phosphorus content of the plants. With sodium 

 nitrate, this was not noted. The solution containing ammonium nit rale also removed more 

 calcium in the drainage water t ban did t lie sodium nit rate. The effect of leaching in increas- 

 ing the availability of rock phosphate is explained on the basis of the mass law. — 11'. ./. Robbil 



299. Gain, Edmond, and Andhk Gain. Conditions thermiques du sol sous l'influence 

 de la vegetation locale. [Thermal conditions of the soil under the influence of local vegetation.] 

 Rev. Gen. Bot. [Paris] 32: 161-164. 1920. A series of measurements showing the degree to 

 which vegetation of various kinds lowers the temperature of the soil at and below the surface. 

 The cooling effect, brought about by the evaporation of water and shading from direct sun- 

 light, varies, in meadows and cultivated fields, from less than 1° to more than 5°. — L. W. Sharp. 



300. Mosseri, Victor M. Note sur les depots Nilotiques des gazayers et saouahel 

 d'Egypte. [Note upon the river deposits upon the islands and the flooded lands along the banks 

 of the Nile in Egypt.] Bull. Inst. d'Egypte 1 : 151-180. 1919. — In accordance with the propor- 

 tion of sand and clay which they contain, the deposits are classified as ramleh (sandy), safra 

 (silico-argilaceous) and soda (argilaceous). On the first only water melons and other cucur- 

 bitous crops and barley are grown; the second produces barley and wheat; while the third for 

 the first year, is either left fallow or is planted to berseem (Trifolium alexandrinum) , which 

 is sown in the mud without preparation; afterwards, it may produce any kind of crop. The 

 ramleh and safra soils, being very permeable, give up their water very readily as the level of 

 water recedes from the surface at the time of the low Nile. The soda (or clay) soils, on the 

 other hand, hold the water much longer. However, when freshly deposited in thick layers 

 it is almost impossible to prepare or cultivate them. In drying they crack enormously. 

 Hence only plants with long tap roots (like berseem) are able to survive injuries caused by 

 cracking and produce profitable crops. At the end of one year, after the fall of the succeed- 

 ing flood, these soils have largely lost their objectionable features. Their fertility however, 

 increases for several years, provided no new deposits of great thickness are made upon them. 

 The defects of these soils are attributed to the large amount of colloidal clay which they con- 

 tain. Among the causes for their gradual improvement, the author considers most important, 

 the appearance in the soils of more concentrated solutions of electrolytes capable of coagu- 

 lating the colloidal clay and thus permitting the loosening of the soil. This concentration of 

 the soil solutions is due to the capillary rise of the subterranean water and its ultimate evapor- 

 ation at the surface. The soluble salts of calcium, chiefly chloride, oppose the formation of 

 carbonate of soda and prevent, by the aeration wdiich they permit, the transformation into 

 this carbonate of alkaline bicarbonates found so abundant in Egyptian soils, w r hich trans- 

 formation renders the soil more or less unproductive. — Geo. F. Freeman. 



TAXONOMY OF VASCULAR PLANTS 



J. M. Greenman, Editor 

 E. B. Payson, Assistant Editor 



GENERAL 



301. Anonymous. [Abstract of: The Thirty-fourth Annual Report of the Watson Botanical 

 Exchange Club for 1917-1918.] Jour. Botany 57: 314-318. 1919. 



302. Anonymous. [Rev. of: Farrer, Reginald. The English rock garden. 2 vol., J+to. 

 Ixiv -f- 504 and viii + 524 P-, 102 pi. T. C. & E. C. Jack: London and Edinburgh.] Jour. 

 Botany 57: 354-357. 1919.— See Bot. Absts. 5, Entry 1792. 



303. B., E. G. [Rev. of: Gamble, J. S. Flora of the Presidency of Madras, Part III. 

 P. 391-575. Adlard & Son.] Jour. Botany 58: 27-28. 1920. 



