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partiality is evinced by vegetables for certain mineral bodies. Chemical analyses and the observa- 

 tions of naturalists assure us of this fact. It is notorious that the plants of salt marshes are distinct 

 from those which are found near fresh waters. In Switzerland, the appearance of certain species of 

 clover is known to indicate marl. The plants indigenous to clays, sands or calcarious soils are 

 distinct, and if they be not instantly recognized it arises from the fact that most lands contain an 

 admixture of all the mineral substances essential to fertility. From the analyses of chemists, now 

 extended to several hundred, we find that there is also evidence of the affinity of plants for certain 

 bases ; thus it is sufficiently clear that Composite, Umbelliferous, Amentaceous, Gramineous and 

 Chenopodiaceous plants prefer potash ; Leguminious, Rosaceous, Solanaceous and Rubaceous plants 

 affect lime ; the families of Cruciferte, Asphodeleae and Liliaceje select soda. Every person knows 

 that oaks, maples and walnuts yield more potashes than pines. The study of this subject is not, 

 however, completed ; there are many points to be considered whicii tend to involve the inquiry in 

 difficulty. It may be said that Davy was the first wlio drew attention to this topic, in a chemical 

 point of view, in the cases of gypsum and clover, oats and silica. Little had Pecn done to this time 

 imtil LiEBiG resuscitating the views of Dundonald and Davy showed the affinity of several 

 plants for certain bases. He enumerates grass, oats, wheat, barley, tobacco, peas, potatoes, clover, 

 corn, turnips and the .Terusalem artichoke. This kind of classification has occupied much of my 

 attention for several years, and has been dwelt upon in my lectures in the University, and for the rea- 

 sons I have already advanced I beg to extend the number of plants to the families above enumerated, 

 in which several are also placed in a situation different from that of Liebig ; the subject is, however, 

 far from decided and probably the exceptions to grouping in families may be greater than the advan- 

 tages gained. Whatever grouping may be expedient, it is not to be forgotten that several circum- 

 stances are to be considered in making use of any analysis for the purpose of determining the place 

 of a plant : these are — 



I. That there exists an unquestionable isomorphism amongst many of the mineral bodies : 

 thus — potash, soda, oxide of ammonium and hydrate of lime — lime and magnesia — sesqui-oxide 

 of iron, sesqui-oxide of manganese and alumina — sulphuric and selenic acids — phosphoric and 

 arsenic acids — are respectively isomorphous groups. Hence soda may replace potash ; hydrate of 

 lime may be present in place of either soda or potash. That this displacement or substitution does 

 occur in nature is abundantly proved. Thus soda has been found to replace the potash of the oak 

 in Long Island, on the sea coast. Marine plants, as the salsosas, transplanted to an inland situation 

 arc found to contain potash. Tobaccos from various 'sources, analyzed by Bertiher, yielded 

 potash as a base, whilst specimens examined by Freseniu.? and Will yielded sixty per cent, of 

 lime and magnesia salts. 



