FATE OF SEEDS INDICATED BY BALANCE 235 



Nearly all his results relating to the diminution of the 

 water-contents of Acacia seeds when kept for years can be 

 explained on the assumption that the oven-experiments were 

 made on seeds in their coverings. The fact that the fresh 

 air-dried seeds sometimes hold as much as 14 per cent, of 

 water sufficiently indicates that the shrinking process was not 

 always complete, and that, as his general table also indicates, 

 they included some permeable seeds, thus accounting for the 

 greater loss of water in the oven. I am inclined to think that 

 the low water-percentages of his old Acacia seeds were due to 

 the experiments being carried out on seeds in their impervious 

 coverings. 



The protection a seed receives from its coats in the oven 

 was not only exhibited in other experiments on impermeable 

 seeds, as in the case of those on the seeds of Canavalia obtusi- 

 folia discussed at the close of Chapter VI., but it was well 

 displayed by the differences in behaviour of permeable seeds, 

 when subjected to the oven test in the entire and in the 

 divided condition, as shown in the results tabulated towards 

 the end of the same chapter. After an exposure of two hours 

 to a temperature of 100 to 110 C., the entire seeds of Pisum 

 sativum, Faba vu/garis, and Phaseolus multiflorus lost 10 or 11 

 per cent, of their weight, whilst seeds of the same set which 

 had been cut across lost 14 or 15 per cent. In the first case 

 the seeds were completely covered by their coats, and in the 

 last case only in part. The seeds were in all cases eight to 

 ten months old. 



It is on these grounds that I venture to differ from Professor 

 Ewart. The future inquirer must decide between us. 



The hygroscopic variation offers a special difficulty in the Permeable 

 examination of the effect of time on the weight of a permeable 

 seed. Notwithstanding that my experiments extend over 



periods of three to four years, it is only safe to say at present the first three 

 11 i -11 i i i'ii or four years, 



that the seeds are still m the hygrometric state which they 



assumed when first entering the resting stage, exhibiting a 

 variation about a mean between the several weighings of about 



