144 SOME EECENT RESEARCHES IN PLANT PHYSIOLOGY 



IMBIBITIONAL FORCES IN DRY SEEDS. 



To measure the capillary and imbibitional forces of air- 

 dry seeds, Shull employed saturated solutions of lithium 

 chloride, which gives the highest osmotic pressure of any 

 known neutral salt. Such seeds contain 8 to 9 per cent, 

 of moisture, and when placed in this saturated solution 

 undergo no permanent change in weight. 



An experiment the converse of the above was then 



43 72 



Hours. 



FIG. 16. CURVE SHOWING Loss OF WATER FROM SEEDS SOAKED IN 

 WATER BEFORE TRANSFERRING TO SATURATED LiCL SOLUTION; 

 IMBIBITION FORCE OF AIR-DRY SEEDS AND OSMOTIC PRESSURE 

 OF SATURATED LiCL SOLUTION APPROXIMATELY EQUAL. 



carried out, for the seeds were first placed in water till 

 they had taken up about 44 per cent, of their dry weight. 

 Being subsequently placed in the chloride solution, which 

 contained the solid in excess to maintain saturation, they 

 rapidly lost weight, so that after 100 hours they re- 

 tained only their original amount of water, as shown by 

 their weight having been recovered. A glance at the 

 accompanying figure permits of the changes being readily 

 comprehended. 



