Physiologie. 357 



In this paper results of over 18,000 determinations of the effect 

 of alkali salts on plant growth are reported. 



Only about half as much alkali is required to prohibit the 

 growth of crops in sand as in loam. 



Crops Vary greatly in their relative resistance to alkali salts, 

 but for the ordinary mixture of salts the following crops in the 

 seedling stage would probably come in the order given, barley 

 being the most resistant: Barley, oats, wheat, alfalfa, sugar beets, 

 corn, and Canada field peas. 



Results obtained in Solution cultures for the toxicity of alkali 

 salts do not always hold when these salts are applied to the soil. 



The percentage of germination of seeds, the quantity of dry 

 matter produced, the height of plants, and the number of leaves 

 per plant are all affected by alkali salts in about the same ratio. 



The period of germination of seeds is considerably lengthened 

 by the presence of soluble salts in the soil. 



The anion, or acid radical, and not the cation, or basic radi- 

 cai, determines the toxicity of alkali salts in the soil. Of the acid 

 radicals used, chlorid was decidedly the most toxic, while sodium 

 was the most toxic base. 



The injurious action of alkali salts is not in all cases proportio- 

 nal to the osmotic pressure of the salts. 



The toxicity of soluble salts in the soil was found to be in the 

 following order; Sodium chlorid, calcium chlorid, potassium chlo- 

 rid, sodium nitrate, magnesium chlorid, potassium nitrate, magne- 

 sium nitrate, sodium carbonate, potassium carbonate, sodium sul- 

 phate, potassium sulphate, and magnesium sulphate. 



The antagonist effect of combined salts was not so great in 

 soils as in Solution cultures 



The percentage of soil moisture influences the toxicity of 

 alkali salts. 



Salts added to the soil in the dry State do not have so great an 

 effect as those added in Solution. 



Land containing more than about the following percentages of 

 soluble salts are probably not suited without reclamation to produce 

 ordinary crops. In loam, Chlorids, 0,3 per cent; nitrates, 0,4 per 

 cent; carbonates, 0,5 per cent; sulphates, above 1,0 per cent. In 

 coarse sand Chlorids, 0,2 per cent; nitrates, 0,3 per cent; carbo- 

 nates, 0,3 per cent; and sulphates, 0,6 per cent. Jongmans. 



Hart, E, B, and W. E. Tottingham. Relation of sulphur 

 Compounds to plant nutrition. (Journ. of Agric. Research. 

 V. p. 233—250. PL 20—22. 1915.) 



The data presented from the greenhouse studies with one type 

 of soil indicate that certain plants are measurably increased in their 

 growth by the addition of sulphates. The authors formerly empha- 

 sized the fact that sulphates have very little effect as compared with 

 soluable phosphates on the soil flora. This difference in action will 

 remove the sulphates from the category of effective fertilizers for 

 all crops. Nevertheless, for certain plants and types of soil they 

 will be beneficial if their only action is as a source of sulphur. 



The plants most affected were the memhers of the Leguminosae 

 and Cruciferae. It is probable that we should expect these classes 

 of plants to be more responsive to the higher concentration of sul- 



