331 



great a drainage prevents the full development of the film, there is an 

 optimum to be aimed at, — an adjustment of the water supply to the 

 drainage, and the production of the rijiht rale of percolation into the 

 soil. Green manuring by increasing the output of gases in the soil, 

 increases the activity of the surface film, and dided by the percolation 

 increases the aeration of the soil in contact with the rice roots. The 

 ploughing in, as we see it in Malaya, of sedges on rice fallows is 

 green manuring. The authors appear to hold that the important 

 benefit to be got from this is the indirect one of aeration at the roots 

 of the rice. 



On page 109 is given an important conclusion arrived at by Mr. 

 C. M. Hutchinson, the Imperial Agricultural Bacteriologist, namely 

 that with such soils as he used for experiment the most rapid and 

 complete nitrification of any given quantity of nitrogenous organic 

 matter could be effected in soil by producing anaerobic conditions 

 with water saturation and subsequently draining and aerating; the 

 rapidity with which nitrification takes place under these conditions 

 depends upon the relative completeness of the anaerobic and subse- 

 quently of the aerobic conditions, i.e., the soil must be open. 



Experimenting with lime, Mr. Hutchinson "found that decom- 

 position of nitrogen-yielding manure was rapid in proportion to high 

 lime content, although in time the soil lower in lime attained the 

 same nitrate concentration". And lime we know goes a long way 

 in keeping a soil open ; but the connection of lime and nitrification 

 is not yet established in detail. 



In connection with forestry it is recorded (pa^ie 120) that " data 

 showed large quantities of tan barks " to be " available in the 

 mangrove forests of Tenasserim and Arakan, that they can be 

 exploited at a reasonable cost, and that the local conditions are 

 generally favourable for the erection of a factory." 



Messrs. Grieve and Shebbeare have drawn attention to the 

 circumstance that the unmixed forests of the Sal tree — SJwrea robusta, 

 Gaertn. — which occur in the Sub-Himalayan tracts of Bengal are 

 there at any rate artificial ; for if fire be withheld an evergreen under- 

 growth asserts itself against which the sal seedings cannot compete 

 in spite of repeated clearings. This Shorea is thus seen to be a 

 pioneer in reafforestation, for it appropriates to itself in time 

 savannahs annually fired. 



Proceedings of the Third International Congress of Tropical Agri- 

 culture, held at the Imperal Institute, London, June 32rd to 30th, 1914. 

 (London John Bale, Sons, and Danielsson, 1914, p. xii-407. Price lOs. 

 net). Abstracts of the papers read at the Congress, and full reports 

 of the discussions are printed in these Proceedings, together with 

 the opening address by the President, Professor W. R. Dunstan. 

 The Transactions of the Congress containing the papers themselves, 

 are in preparation. 



