IN SAND 51 



made by the author (10). The toxic limits of wheat for 

 salts in a sand were as follows: sodium chloride with 12 

 per cent moisture 2900 parts per millon, with 18 per cent 

 5700 parts per million; sodium carbonate with 12 per cent 

 2700 parts per million, with 21 per cent 3300 parts per 

 million; sodium sulphate with 12 per cent 8000 parts per 

 million, with 24 per cent 16,000 parts per million. When 

 the salts were added dry to the soil rather than in solution 

 as in the above experiments, the limits of tolerance were 

 higher, but the quantity of moisture added to the soils 

 would influence the permissible quantity even more in 

 such experiments than where the solutions were added be- 

 cause the quantity dissolved would be more dependent on 

 the water present. 



In the work of Buffum and Slosson (4) sand was used as 

 the medium for growing seed in a nutrient solution, an 

 attempt being made to duplicate soil conditions as nearly 

 as possible. Their work was with wheat and alfalfa in 

 sand containing solutions with osmotic pressure equivalent 

 to 2.03, 3.80, and 7.10 atmospheres which corresponds to 

 5000, 10,000, and 20,000 parts per million of sodium sul- 

 phate, or 2700, 5100, and 9700 parts per million of sodium 

 chloride. The conclusions were that the lower concentra- 

 tions of the salts were stimulating to the plants bu'c that 

 the higher ones were harmful. Solutions of sodium sul- 

 phate, potassium sulphate, sodium chloride, and potassium 

 chloride were all about equally harmful to those plants at 

 the same osmotic pressures when based on germination 

 and several other observations of the growing plants. 



A series of germination experiments in a sand by Stew- 

 art (28) showed that 10,000 parts per million of sodium 

 sulphate was generally fatal to seeds of barley, rye, wheat, 

 oats, peas, alfalfa, and red and white clovers. The re- 



