588 Journal of Agricultural Research vol. xx.No. 7 



and Cameron 1 found, for instance, that when 50 gm. of seeds of cowpeas 

 were mixed with 50 gm. of soil containing 15 per cent of water, the 

 seeds had in 12 hours gained 12.1 per cent of water and had left in the 

 soil only 1.3 per cent — that is, the soil was reduced practically to air-dry 

 condition. It appears, therefore, that the power of seeds to absorb 

 water is very much greater than that of soils. Some attempts have 

 been made to measure the magnitude of the initial attraction that seeds 

 possess for water. Especially notable is the work in this direction of 

 Shull 2 who attempted to measure the attraction of seeds of Xanthium 

 for water, and then he used these seeds to measure in turn the moisture- 

 holding forces of soils. Shull found that the air-dry seeds of Xanthium 

 show an initial attraction for water of nearly 1 ,000 atmospheres. 



Since it was found that soils cause water to become unfree, the extent 

 varying with the character of the soil, the question arose whether the 

 seeds also cause water to become unfree, and if so, to what extent. It 

 was reasoned and anticipated that since seeds possess a greater attraction 

 for water as evidenced by their power to abstract moisture from the 

 soil itself even down to the point of dryness, they ought to cause a 

 larger amount of water to become unfree. 



In order to obtain information bearing upon these questions a general 

 investigation of the problem was undertaken. The type of dilatometer 

 used and the general procedure followed were the same as those used in 

 the study of soils. The procedure consisted in weighing out carefully 

 about 10 gm. of air-dry seeds and placing them in water to soak for 

 about two days. Then they were taken out, pressed between filter papers 

 in order to eliminate their excess of water, weighed again quickly, and 

 introduced into the dilatometer. The unoccupied space in the dilatom- 

 eter was then filled with ligroin, and care was taken to expel all the 

 air. The mouth of the dilatometer was then carefully stoppered, and the 

 contents were placed to cool in a temperature of — 3 C. When this 

 temperatuie was attained by the contents, as indicated by the column of 

 ligroin in the stem, which remained stationary, the water in the seeds was 

 caused to freeze. This was accomplished by taking hold of the dilatom- 

 eter by the stem and moving it gently in the cooling mixture until 

 solidification began, which was indicated by the rise of the ligroin in the 

 stem. The dilatometer was allowed to remain in the cooling mixture 

 with frequent movements until the rise of the ligroin in the stem ceased. 

 The total rise of the ligroin in the stem was taken to represent the total 

 amount of expansion due to the formation of ice. 



In order to determine the effect of repeated freezing or of lower tempera- 

 ture upon the amount of water that seeds cause to become unfree, the 



1 Whitney, Milton, and Cameron, F. K. investigations in soil fertility. U. S. Dept. Agr. Bur. 

 Soils Bui. 23, p. 30. 1904. 



2 Shull, Charles Albert, measurement of the surface forces in soils. In Bot. Gaz. v. 62, no. 1, 

 P- 1-3 1. 5 fig- 1916. Literature cited, p. 29-31. 



