1 9 14] CROCKER & DA VIS— DEL A YED GERMINA TION 3 1 7 



This has been a standing assumption for a long time, but an assump- 

 tion not backed by evidence. The claim has received lately most 

 telling counter-evidence by the work of Brown (5), Schroder 



from which it aDDears that sem 



membranes are of rather common 



We 



mem 



brane in the coat of Alisma. We 



njured by many days' soaking in 1 mol. copper 

 mbryo will not grow markedly in a 0.001 mol 



same 



The conclusions drawn in this paper must be applied only to 

 Alisma seeds, but it will be surprising if they do not hold for the 

 very similar seeds of Sagittaria, and for the less similar seed of 

 Eichhornia, and perhaps for the seeds of many water plants. 



The power of acids to hasten the germination of the haw must 

 not be identified with the forcing effects in Alisma. In the first 

 case, the effect is on the dormant hypocotyl itself, and in the second, 

 on the coat in the main. In the first case it is hardly necessary 

 to confuse the matter by calling the effect a stimulus, and in the 

 second such an explanation is quite aside from the point. 



The peculiar effect of copper sulphate solutions on the germina- 

 tion of acid-treated intact seeds shows the danger of assuming 

 that such effects of salts are on the embryos rather than the coats 

 when intact seeds are used. 





We wish to express our gratitude to Dr. Sophia Eckerson for 

 most of the microchemical determinations reported in this paper. 



V. Summary 



ormancy 



mechanical restraint of the seed coat. This restraint enables the 

 seed to be in water for years without germination. 



2. The chaffy carpel wall plays no part in the dormancy. Of 

 the three layers of the seed coat (the outer single layer of reddish- 

 brown cells, the inner single layer of white cells, and the lining 

 acellular pectic hemicellulose material), the outer seems to play no 



