ATMOSPIlEllIO Alli AS TIIK P<)01» OF PLANTS. 



their command, besides that contained in the seed itself, 

 should be the free nitrogen of the atmosphere. For tliis 

 purpose he prepared a soil consisting of pumice-stone and 

 the ashes of stable-manure, which was perfectly freed from 

 all Compounds of nitrogen by treatment with acids and in- 

 tense heat. In nine of his earlier experiments the soil thus 

 prepared was placed at the bottom of a large glass globe, 

 j5, fig. 4, of 15 to 20 gallons' capacity. Seeds of cress, 

 dwarf beans, or lupins, were deposited in the soil, and a 

 proper supply of water, purified for the purpose, was add- 

 ed. After germination of the seeds, a glass globe, D, of 

 about one-tenth the capacity of the larger vessel, was filled 

 with carbonic acid (to supply carbon), and was secured air- 

 tight to the mouth 

 of the latter, com- 

 munication being 

 had between them 

 by the open neck at 

 C. The apparatus 

 was then disposed in 

 a suitably lighted 

 place in a garden, 

 and left to itself for 

 a period which va- 

 ried in the diiferent 

 experiments from 1^ 

 to 5 months. At 

 the conclusion of the 

 trial the plants were 

 lifted out, and, to- 

 gether with the soil 

 from Avhich their roots could not be entirely separated, 

 were subjected to chemical analysis, to determine the 

 anfiount of nitrogen which they had assimilated during 

 growth. 



The details of these trials are contained in the subjoined 



