GRAINS AND OTHER SEEDS 179 



The gas thus absorbed has a marked influence upon 

 the germination of the seeds and upon the subsequent 

 growth of the seedlings. In these experiments it was 

 found that some of the seeds were able to resist for 

 more than three hours the influence of the gas from 

 0.25 gramme of potassium cyanide per cubic foot, al- 

 though after three hours 50 per cent, of the seeds were 

 unable to germinate and the other half were held in 

 check for forty-eight hours beyond the usual time of 

 germination. However, the seeds that did germinate 

 produced seedlings that grew at the normal rate. If 

 the grains or seeds are dry, the influence of the gas is 

 far less marked than if they are moist, and the drier 

 they are, the less they are influenced by the gas. 



It would seem, therefore, that the gas exerts its in- 

 fluence through the medium of the moisture contained 

 in the seeds and in the seedlings. Even in older plants 

 it is the more succulent parts that are most readily af- 

 fected by the gas. The seed-coats serve more or less 

 as a protection for the inner seed parts, and as soon as 

 the seedlings escape from the seed-coats they are more 

 seriously affected by the gas, and if the charge is suf- 

 ficiently strong the seedlings refuse to grow almost as 

 soon as they leave the seed-coats. Dry seeds are suf- 

 ficiently resistant to the influence of hydrocyanic acid 

 gas to be treated for several weeks with an atmosphere 

 saturated with the gas without destroying their vital- 

 ity. It would be impossible, however, to preserve 

 even dry seeds indefinitely in any strength of the gas, 

 since it eventually penetrates the dry seeds and im- 

 pairs and finally destroys the vitality of the seeds. If 

 the seeds are damp they are much more susceptible to 



