NUTRITION. 79 



that the principles found in the plants themselves bear 

 to those of the soil in which they have grown, for sub- 

 stances have been said to have been found in plants 

 which never could have been taken from the soil ; it 

 has therefore been thought that plants, by virtue of the 

 vital powers of nutrition, could form certain inorganic 

 products out of the elements of others taken in by them. 

 This is now supposed not to be the case, but, on the 

 contrary, that all the inorganic bases of the matters 

 found have been absorbed by the plant, and not pro- 

 duced within them. 



42. It has been said that plants might be grown in 

 any thing as a soil, and the experiments of Schrader, 

 Braconnot, and Sukkow, are adduced as examples ; in 

 their experiments seeds were said to have germinated in 

 sublimated sulphur, sand, silver tinsel ; and on slips of 

 paper, old books, &c., by Bonnet : and though in the 

 former cases, only moistened with distilled water, or- 

 ganic and inorganic substances increased within the 

 plants ; the later experiments of Lassaignes, Jablonski, 

 and others, have proved that under these conditions it 

 is only up to a certain period that the life of the plants 

 so produced can be maintained, and that is dependent, 

 not upon the soil, but upon the plants' own reservoirs of 

 nutritious matter. 



43. Latterly considerable light has been thrown upon 

 the knowledge of soils in general, by Boussingsalt. It 

 is universally known, as a general rule, that all plants 

 will thrive better in good garden mould than in a 

 common field, unless the latter contains some particular 

 ingredient for which a plant has a marked affinity ; and 

 Woodward and Kylbel have shown that garden mould 

 contains a particular extractive matter, a source of 

 very great nourishment to the plant growing in it. 

 From analysis of this mould, which has its origin in the 

 decomposition of various vegetable matters, it has been 

 stated to consist of earthy extract, earthy acid, earthy 

 carbonaceous matter, besides saline ingredients ; the 

 quantity of the extract in good garden mould was 10 to 4. 



