of Organic Bodies. 3 



The Inorganic Constituents of Plants. 



Plants obtain their inorganic constituents by means of the 

 roots, which derive them from the soil upon which they grow. 

 The latter either already contains them among its constituents, 

 or they are added to it in a suitable manure. In both cases 

 these inorganic constituents exist in the highest possible state 

 of oxidation. If they are not contained in the manure in this 

 state, the latter is not in a perfectly proper condition, and does 

 not become so until it has been exposed to the air for some 

 time. 



It may certainly be admitted, that the inorganic constituents, 

 absorbed by the root in the most perfect state of solution pos- 

 sible, ascend in the vessels of the stem. Probably those salts 

 which are insoluble in water are dissolved by the aid of car- 

 bonic acid. 



During the growth of the plant a deoxidizing process goes 

 on within it ; the green parts under the influence of solar light, 

 as is well known, evolve oxygen gas. Even when they only 

 decompose the carbonic acid of the air, they assimilate its 

 carbon ; hence the amount of the latter in the plant gradually 

 increases in proportion to that of the oxygen. All those parts 

 of the plant which are in contact with the green parts take a 

 share in this deoxidizing process, so long as it continues in a 

 state of growth and the green parts have not lost their green 

 colour. Now when we find that in plants one portion of the in- 

 organic constituents absorbed by the root exists in a deoxidized 

 state, in which, at least after the carbonization of the plant, it 

 is insoluble in the ordinary solvents — water and muriatic acid, 

 and that this portion is not converted into the same salts as 

 those absorbed by the root from the soil until after oxidation, 

 it may be supposed that the quantity of deoxidized inorganic 

 constituents must be small in those parts of the plant which 

 are in more immediate contact with the soil, and in which, 

 therefore, the deoxidation of the parts of the plant, and also 

 that of the inorganic salts existing in them, first commenced. 

 But this quantity must be greater in those parts of the plant 

 the formation of which has required the longest time ; and 

 after the formation of which, many plants, including all the 

 annuals, die. Hence the proportion of the inorganic consti- 

 tuents of the plants which are deoxidized to that of those which 

 are not deoxidized, must be very different in the herbaceous 

 portions of the plant and the seeds. 



This supposition has been most completely verified by ex- 

 periment. 



M. Weber made a comparative experiment upon the inor- 



B2 



