BOTANICAL GAZETTE 



[JULY 



apparatus would in no way change the nature of the conclusions 

 to be drawn from the results. 



IV. Experimental results 



A. Measurement of the seeds. — The measurement of the 

 internal forces of Xanthium seeds by means of NaCl and LiCl 

 solutions has been repeated and extended with full confirmation 

 of the previously published results. The data are presented in 

 tabular form for the sake of convenience in table III, and these 

 figures may serve as a basis of comparison in the soil experiments, 

 where the surface forces of the soil particles, instead of osmotic 

 pressure, are pitted against the internal forces of the seed. The 

 data were secured with the lower seeds of Xanthium pennsyhanicum. 



Moisture intake of Xanthium seeds in osmotic solutions; temperature 



2 3-5° C.; INTAKE IN PERCENTAGE OF AIR-DRY WEIGHT 



The results obtained by the vapor pressure method over sul- 

 phuric acid are shown in table IV, and some of the curves of 

 moisture intake showing the point of natural equilibrium are shown 

 in figs. 2 and 3. 



As the table and curves show, the seeds are initially in moisture 

 equilibrium with sulphuric acid of 46-54 per cent strength. In 

 general the seeds which have carbohydrate reserves in greatest 



