Jan. 3. 1021 Amount of Unfree Water Caused by Seeds 591 



wheat, corn, barley, and rye the process of repeated freezing and thaw- 

 ing had very little effect if any on the unfree water. 



The process of repeated freezing and thawing, therefore, has practically 

 the same influence in seeds as it has in soils. In both cases it tends to 

 diminish the amount of unfree water in some seeds or soils more than in 

 others. 



In explaining the decrease of the unfree water by repeated freezing 

 and thawing two hypotheses were presented. In the one it was sug- 

 gested that part of the water is held by the capillarities of the soil and 

 does not freeze. Upon repeated freezing and thawing these capillarities 

 are destroyed, and the water they held is liberated or becomes free and 

 freezes readily. 



In the second hypothesis it was assumed that soils such as clays, clay 

 loams, silts, muck, and peats contained a considerable amount of colloidal 

 material which held water in such a manner that it does not freeze. 

 Upon repeated freezing and thawing, however, these colloids are coagu- 

 lated or destroyed, and the water they held is liberated or becomes free 

 and readily freezes. 



These suggested explanations with few modifications may apply also 

 to seeds. There is no doubt that the living tissue as well as its capil- 

 laries and colloidal material are affected or destroyed by severe freezing. 



It may be of interest to record here that when very old corn seed was 

 employed or corn seed that had been frozen in the field, no water was 

 caused to become unfree. Apparently long age or previous freezing 

 of the corn seed destroyed its power to cause water to become unfree. 

 This phenomenon, however, did not appear in the other seeds. 



According to the classification of moisture in the soils based on the 

 dilatometer method, the water which freezes after the first freezing 

 may be classified as capillary-adsorbed water, while that which refuses 

 to freeze after the fourth freezing and at the low temperature may be 

 classified as combined, probably in the form of water of hydration and 

 water of solid solution. 



However, the division of the unfree water into capillary adsorbed and 

 combined water is probably not so sharp in seeds as in soils, because in 

 the seeds there is a considerable quantity of water-soluble material 

 which causes a high freezing-point depression, and this in turn decreases 

 the amount of water that freezes at the degree of supercooling employed. 

 As is well known, there is always a tendency for an equilibrium to be estab- 

 lished between the liquid-solvent, solid-solvent, and the solute at any 

 temperature below freezing until the cryohydric temperature is reached. 

 Some of the water, therefore, which refused to freeze at — 20 C. or which 

 froze and melted again at — 3 may be due to the water-soluble material 

 of the seeds. It is believed, however, that the amount of water that 

 was prevented from freezing by the high freezing-point depression of the 

 seeds is probably not very great. 



