66 Kansas Academy of Science. 



greater than the internal force of the seeds, moisture would 

 pass from the seed to the soil, increasing the thickness of the 

 surface films of the soil particles and thereby decreasing their 

 surface attraction for water, while the internal forces of the 

 seed increase as in the previous case. Finally, where the seed 

 possesses a semipermeable coat, and lies in an osmotic solution 

 whose pressure is greater than the internal forces of the seed, 

 water is extracted from the seed, which dilutes the osmotic 

 solution and lowers its force, while, as before, the internal 

 force of the seed increases rapidly as it loses water. In each 

 case the movement of water continues only until the two 

 forces, unequal at the start, become equal. This establishes 

 moisture equilibrium, and further movement of water must be 

 consequent to some disturbance, either external or internal, 

 of the balanced condition of the forces. It is because of this 

 relationship of the forces to water itself that the seed under 

 natural conditions never becomes absolutely dry. For as it 

 approaches dryness, the internal forces of the seed far exceed 

 the evaporating power of the driest natural atmosphere. 



Few attempts have been made to measure the magnitude of 

 the internal forces of the hydrogels that make up the seed. 

 The measurement of forces which cause the entry of water 

 into absolutely dry organic matter has been attempted, the 

 values being calculated from the amount of heat released dur- 

 ing imbibition. Such release of heat energy during imbibition 

 was probably first observed by Pouillet. As early as 1865 

 Jungk suggested that the liberation of heat by finely divided 

 bodies, on being wet, was due to a compression or condensa- 

 tion of the fluid by the surface force of the fine particles. 

 Oven-dried starch, for instance, on being wet with water of 

 the same temperature, often shows a rise of 10 to 12 degrees. 

 It is estimated that a rise of .03° C. requires about 34 atmo- 

 spheres of pressure, so that a rise of 11 degrees indicates a 

 surface force far exceeding 10,000 atmospheres on the par- 

 ticles of absolutely dry starch. 



Lagergren, in 1898, found that a gram of powdered charcoal 

 having 4 meters of internal surface required about .224 g. of 

 water to wet it, and that a little over 8 calories of heat was 

 liberated by the wetting process. If a whole gram of water 

 were to be used with as large a mass of charcoal as it could 

 wet, the heat liberated from that one gram of water would be 



