24 



not an accident of the method of collection. It is difficult to under- 

 stand why the summer rain should contain less oxygen than rain 

 falling in the rest of the year, especially in view of the circumstance 

 that the relative temperatures of the rain clouds and of the air at 

 ground level ought to cause super-saturation in summer and notunder- 

 saturation. 



The significance of the dissolved oxygen in the soil is discussed. 



IV. " Methods for the Examination of Soil Protozoa. Charles 



Henry Martin and Kenneth R. Lewin. Journal of 

 Agricultural Science, 1915. 7, 106-119. 



Descriptions are given of some of the organisms isolated in the 

 trophic state by the two methods already described (Annual Report for 

 1914, page 19). Amoebae and thecamcebae w^re most frequently met 

 with ; ciliates and flagellates* were relatively rare. 



The organisms described are Euglypha and Chlamydophrys among 

 the thecamcebae ; Chilodon, a ciliate ; Vahlkampfia soli, a Umax 

 amoeba, Amcsha gobaniensis and AmcBba cucumis, lamellipodian amoebae, 

 and Boda caudatus, a flagellate ; all these had been found in the trophic 

 state in the soils examined. 



V. " Soil Protozoa and Soil Bacteria.^'' E. J. Russell. Proceed- 



ings of the Royal Society, 1915. 89, 76-82. 



The experimental evidence of the existence in soil of a livmg 

 protozoan fauna in the trophic, as distinct from the encysted, state 

 is collected. The fauna is shown mainly to consist of flagellates, 

 amoebae and thecamcebae ; ciliates only being present in smaller 

 numbers, and probably for the most part in the enc3^sted form. This 

 conclusion is in harmony with Goodey's w^ork, and with all the facts at 

 present ascertained. 



VI. " The Utilisation of Organic Residues for Nitrogen Fixation 



and the Losses of Nitrogen from the Soil.^' Henry 

 Brougham Hutchinson. Journal of Agricultural Science, 

 1918. 9, 92-111. 



It has long been known that appreciable quantities of gaseous 

 nitrogen may be assimilated from the atmosphere when a soil or a 

 culture of a soil organism (Azotobacter chroococcum), is supplied with 

 soluble carbohydrates under laboratory conditions. The present 

 paper shows that this action also occurs under natural conditions, and 

 that plant residues can be utilised for nitrogen fixation in the labora- 

 tory and in pot experiments. Crop increases may also be obtained 

 when field soils are treated with an easily oxidisible carbohydrate 

 such as sugar, and these may be attributed to the assimilation of 

 atmospheric nitrogen. 



The effect of carbohydrates and of plant residues on the soil is 

 shown to be complex, and under certain conditions — when the soil 

 temperature is low, or when the appHcations are made too near to the 

 time of sowing — marked depression of the crop may occur. This 

 effect appears to be largely due to destructive processes, which result 

 in a withdrawal of available nitrogen compounds or a loss of free 

 nitrogen from the soil. 



*Hubf)e(iutint work has nhowii that ain(plui> and thccaiiKrbee are much more numerous than 

 dilates, thouuh, as a matter of fact, the na^ellatf'S arc often more numerous still— not 

 luHM HO an thc-e earlier ohservutions suKpested. 



