GERMINATION. 27 



vorable they may be in reference to humidity and temperature. 

 Some formation of carbonic acid is indeed to be observed under 

 such circumstances, but then this gas is the result of the decompo- 

 sition and putrid fermentation of the seed. It is therefore by means 

 of the oxygen which it contains, that atmospheric air concurs in the 

 germination of seeds. 



Rollo was the first who ascertained the production of carbonic acid, 

 during the germination of seeds in an atmosphere of oxygen ; but it 

 was M. Theodore de Saussure, who by delicate eudiometrical ex- 

 periments, demonstrated the phenomena in all their nicety, by prov- 

 ing thai the oxygen consumed was replaced by a corresponding 

 volume of carbonic acid.* 



There are some seeds, for instance, peas, and the seeds of aquatic 

 plants, which have the property of germinating under water. Some 

 observers have, from this fact, come to the premature conclusion that 

 atmospheric air, and consequently oxygen, were by no means neces- 

 sary to germination. Saussure has explained this anomaly by re- 

 ferring to the constant presence of air in a state of solution in water. 

 In fact, having placed some seeds of the polygonum amphibium under 

 water, deprived of its air by long boiling, Saussure proved that ger 

 mination could not take place. f 



Under like circumstances, the quantity of carbonic acid generated 

 in a given time, is by so much greater, the larger the quantity of 

 oxygen in the atmosphere which immediately surrounds the ger 

 minating seed. Carbonic acid gas is, of all the gases which have 

 been tried, that which is most unfavorable to germination ; and one 

 way of hastening the process is to place under the receivers which 

 cover the seed, some substance capable of absorbing it as fast as it is 

 formorl — quick-lime, for example. By this arrangement the radic- 

 ular increase is sensibly accelerated, J 



The quantity of oxygen gas necessary to germination, is not the 

 same in reference to all seeds ; lettuce, the french-bean, and the 

 field-bean require about yg^th part of their respective weights ; while 

 J^th less is sufficient for wheat, barley, purslane, &c. Saussure 

 moreover came to the conclusion that the carbonic acid generated 

 by these diflferent seeds in germinating is proportioned to their mass, 

 and altogether independent of their number.^ 



Inasmuch as seeds during germination yield carbonic acid to the 

 atmosphere, it is quite obvious that they must lose some part of their 

 original weight. And this they do in fact ; but the loss experienced 

 by seeds which have germinated is always greater than that which 

 would have resulted from the destruction of carbon that takes place. 

 Saussure attributed this excess of loss to the volatilization of a por- 

 tion of the water which entered into the composition of the seed.jj 

 According to Saussure, therefore, the phenomena of germination 

 resolve themselves into the diminution of carbon and of the elements 

 of water. It is, nevertheless, doubtful whether the chemical actions 



* Saussure, Recherches chimiques sur la V6g6tation, p. 10. 



t Idem, p. 3. t Mem, p. 26. $ Idem, p. 13. ^| Idem, p. ao. 



