1909.] Coverings of the Seeds q/Hordeum vulgare. 85 



taining from 2 to 32 grammes of salt per 100 grammes of solution are 

 recorded graphically in the accompanying diagram. 



29 



Hours of steeping. 

 JO 40 SO 6 70 



80 30 





50 





45 







a> 







40 



j= 





-p 









a h 



3S 



■a 





u 



p 





E 



30 



<A 













■§ 



2S 



is 









O 





© 





bD 



20 















o 

 s- 



IS 







Pa 







10 



































































































" 



































1 







































f/ 







Satu 



IATED 



SOLU 



riON c 



if Sal 



r 





If 





















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It will be noticed that the amount of water absorbed by the seeds when 

 equilibrium is established is less the more concentrated the solution, as it 

 varies from about 14 per cent, in the case of a saturated solution to about 

 41 per cent, in the case of a solution containing only 2 per cent, of salt ; 

 this latter amount is much below that absorbed when the seed is steeped in 

 water alone (over 70 per cent.). 



It should be pointed out that the determinations on which the curves are 

 based are affected by an unavoidable error due to the manner in which the 

 values are arrived at. Some allowance should be made for the amount of 

 water absorbed by the outer covering of the seeds. It is not possible to 

 evaluate this amount very closely ; apparently, however, it may be taken as 

 equal to about 8 per cent, of the original weight of the dry seed. Making 

 the extreme assumption that the amount absorbed by the outer covering is 

 independent of the concentration of the solution, the quantity absorbed by 

 the starchy contents of the seed from a saturated solution of salt is only 

 about (14 — 8 =) 6 per cent, calculated on the weight of the dry seed. It 

 appears, therefore, that the power of the seed contents of attracting water 

 from a saturated solution of salt exceeds the osmotic attraction of the latter 

 to only a slight extent ; as the " osmotic pressure " of a saturated solution 



