(;. A. CowiE 123 



0. Loew(i7) observed a gradual withering of the leaves from the tips 

 downwards in young barley plants grown in a nutrient solution con- 

 taining 0-5 per cent, dicyanodiamide. In a 0-2 per cent, solution, on the 

 other hand, Elodea was not only not injured but it assimilated and used 

 the dicyanodiamide as a source of nitrogen. In a later investigation 

 Loew concluded that (1) in a sterilised soil dicyanodiamide and am- 

 monium sulphate were equally effective in grain formation, (2) in an 

 unsterilised soil, on the other hand, barley makes little growth: this 

 difference was attributed to injurious substances formed from the 

 dicyanodiamide by bacteria, (3) the withering of the tips of the leaves 

 was attributed to an accumulation there of dicyanodiamide. 



ill water-culture K. Aso{i8) found dicyanodiamide at the concen- 

 tration of -01 per cent, served as a source of nitrogen for plants. In 

 soil, however, it was toxic at the rate of 5 grams in 10 kilos soil but had 

 good effects in smaller quantities. 



Inouje(i9) obtained similar results: dicyanodiamide at the rate of 

 1 gram N per 8 kilos soil was injurious especially to the young plants, 

 while at one-third this rate it was beneficial. 



A. Stutzer and F. Reis(2n) found that dicyanodiamide had a marked 

 injurious effect on the germination of both oats and barley. In pot 

 experiments using quartz sand, dicyanodiamide at the rate of 30-45 

 kilos per hectare proved highly deleterious to various plants. Maize 

 grown in loam gave only one-tenth of the yield with dicyanodiamide as 

 with nitrate. 



In pot experiments by Ch. Brioux(2l) dicyanodiamide at the rate of 

 50 kilos N per hectare depressed the yield of buckwheat 50 per cent, 

 below that of the controls without nitrogen in one case and 37 per cent, 

 in another. Like Immendorff he noted the withering of the tips and 

 margins of the leaves of the treated plants. 



E. Truninger(22) found that the injurious influence of dicyanodiamide 

 at an early stage could be largely overcome by the simultaneous 

 application of a readily assimilable nitrogen compound. He was 

 disposed to attribute the unfavourable influence of dicyanodiamide to 

 its great stability in the soil, as no nitrification was evident after two 

 months. 



Pfeiffer and Simmermacher(23) have shown in a recent paper that 

 a gradual rise in the proportion of dicyanodiamide nitrogen in the 

 nitrogenous dressing above -16 gram in 15 kilos soil resulted in in- 

 creasing amounts of injury to the plants and corresponding reduction 

 in the yield of oats grown in pots. The germination, however, was not 



