CAUSES. 35 



cumstances, require twelve. Adanson found that many 

 seeds which were transported from Paris to Senegal 

 germinated three days earlier than in their native coun- 

 try. And wherever it is desirable to obtain the earli- 

 est productions of the season, seeds ripened in a north- 

 ern climate should be selected, for though less luxuri- 

 ant, plants which are thus obtained, reach maturity with 

 a less degree of heat. Since the agency of oxygen be- 

 came known, it has been ascertained that it may be 

 employed to excite the vegetative power of seeds, 

 which under common circumstances refuse to grow. 

 At least those substances which yield it with facility and 

 in abundance, have been employed with the greatest 

 success to produce this very desirable effect. One of 

 the most effectual of these is, the chlorine of modern 

 chemistry. Humboldt,* to whom we are indebted for 

 this discovery, planted some Cress seeds in sand, and 

 moistened some of them with pure water, and others 

 with water impregnated with chlorine ; the latter vege- 

 tated in six, the others in thirty-six hours. Jacquin 

 employed the same agent to excite the action of seeds 

 which he had received from the cape of Good Hope, 

 and though every other effort had proved ineffectual, 

 this was crowned with the most flattering success. 



It has been a question whether light promotes or re- 

 tards germination. However important it may be to 

 the luxuriance of the growing plant, I am inclined t® 

 believe that its influence on the germinating seed is 

 comparatively trifling. It seems to have been the de- 

 sign of nature, that this operation should be performed 

 in the bosom of the earth, secluded from the light of 



* Humboldt mixed about four parts water with two of manga- 

 nese and one of common muriatic acid, and placed the seeds in 

 this mixture until the rostel was evolved. 



