112 JOURNAL OF FORESTRY 



To meet the criticism that friction retards the movement of water 

 in dry soils, and that consequently the seeds do not reach equilibrium 

 with the total soil mass, but only with soil near them, Shull devised 

 a rotating method which brings the seeds constantly into contact with 

 fresh soil particles. 



Moisture Intake of Xanthium Seeds in Osmotic Solutions; Temperature 23.5° C. 

 Intake in Percentage of Air-dry Weight 



The principal sources of error, Shull states, are due to the impos- 

 sibility of handling seeds in ordinary atmospheres without some loss 

 by evaporation, and to the lower accuracy of hot-air ovens for drying 

 as compared with vacuum driers. But every precaution was taken 

 to reduce errors to a minimum, and Shull confidently believes that 

 more refined methods would in no way change the nature of the con- 

 clusions drawn from the results. 



The tests were confined to the region of soil moisture between air- 

 dry and the wilting coefficient because in soil with a higher moisture 

 content the seeds always became saturated. This alone is striking 

 evidence of the significance of the wilting coefficient. 



Most of the work was done with two soils, Oswego silt loam, a 

 heavy soil with a moisture equivalent of 35.2 per cent and a wilting 

 coefficient of 19.1 per cent, and a fine quartz sand with a moisture 

 equivalent of 2.41 per cent and a wilting coefficient of 1.3 per cent. 



For the Oswego silt loam he gives the results of 4 series of tests 

 running from air-dry to approximately 20 per cent. 



Exact comparison between the series is rendered a little difficult 

 by the lack of regularity in the percentages of soil moisture. For 



