17 



mosphere ; but neither in pure hydrogen nor nitro- 

 gen did the process at all go on *. 



15. M. Huber proceeded next to ascertain the 

 smallest quantity of oxygen that would suffice for 

 germination. He found, that seeds did not grow in 

 very small volumes of air ; and that the greater the 

 number of seeds confined in a given volume of air, 

 the more was their growth retarded ; that where the 

 oxygen gas constituted only one-eighth of the atmos- 

 phere, no effect was produced on lettuce-seeds, but 

 that one-sixth of it began to promote their growth. 

 Lefevre, however, is said to have found, that an at- 

 mosphere containing only ~ part of oxygen, favour- 

 ed the evolution of raddish-seeds, which renders it 

 probable that different seeds vary much in the pro- 

 portion of oxygen necessary to carry on their ger- 

 mination | When the atmosphere was impregna- 

 ted with the vapour of sulphuric ether, of camphor, 

 spirits of turpentine, assa-fcetida, vinegar and am- 

 monia, the process of germination was more or less 

 retarded. From the facts stated in this and the pre- 

 ceding paragraph, we learn, not only that air is ne- 

 cessary to the growth of seeds, but that the ordi- 

 nary state of its composition in our atmosphere is, 

 as M. Sennebier observes, the best adapted to pro- 

 duce a vigorous germination. This state, however, 

 is not determined with such rigour that a small va- 

 riation in the proportions or qualities essentially in- 

 jure the process : it admits, on the contrary, of great 

 latitude without much disturbance, which provision 



* Sur la Germination, p. 58. f Ibid. p. 64% et seq. 



B , 



