68 Kansas Academy of Science. 



when its hygroscopic equilibrum was represented by 7 per 

 cent of moisture, had an initial internal pressure of but little 

 less than a thousand atmospheres (965), or more than 14,000 

 pounds per square inch. When the moisture content of the 

 seed has been increased until it amounts to about 14 per cent 

 of the absolute dry weight of the seed (about 7 per cent beyond 

 the ordinary hygroscopic moisture) the internal force is a 

 little less than 400 atmospheres at ordinary temperatures. 

 And so the internal force could be determined for any par- 

 ticular moisture content. 



The assumption is made that moisture equilibrium results 

 from the interplay of forces which actually become equal 

 when equilibrium is attained. In other words, I am assuming 

 that the total osmotic pressure is transmitted as force when 

 pitted against the internal force of the seed. While definite 

 proof as to the validity of this assumption can not be offered 

 at present, there is some supporting evidence, and unless or 

 until it is shown to be erroneous it is believed to be justified. 



Obviously, this method of measurement can be applied only 

 to seeds which have perfectly semipermeable coats. But many 

 seeds have permeable testas, or possess an open micropyle; 

 which makes the application of such a method impossible. A 

 new method of measuring the internal forces of seeds is now 

 being perfected which can be applied to any seed regardless 

 of the character of the coat. It is based on the assumption 

 that osmotic pressure can be computed from vapor pressure — 

 an assumption whose validity is admitted by practically all 

 physicists and physical chemists — and that the vapor pressure 

 of the seed hydrogels measured against the vapor pressure of 

 strong solutions is a true measure of the internal force of the 

 seed. Although not proven valid, this second assumption 

 seems as reasonable as the first; and in actual practice the 

 values obtained for the internal forces of the seed colloids by 

 this method are fairly concordant with those obtained by the 

 osmotic-pressure method. 



This method consists of suspending the air-dry seeds in an 

 enclosed atmosphere over a series of sulphuric acids of varying 

 strengths from very dilute to the pure acid as obtained from 

 the stock bottles, i. e., acid of about 1.83 specific gravity. Over 

 the dilute acids, where the vapor pressure is relatively high, 

 the seeds imbibe moisture because their own vapor pressure 



