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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 Cruciferse, Asphodelese and Liliacese 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 which tend to involve the inquiry in 
difficulty. It may be said that Davy was the first who drew attention to this topic, in a chemical 
point of view, in the cases of gypsum and clover, oats and silica. Little had been done to this time 
until 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 Jerusalem 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— 
1. 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 
are found to contain potash. Tobaccos from various sources, analyzed by Berthier, yielded 
potash as a base, whilst specimens examined by Fresenius and Will yielded sixty per cent, of 
lime and magnesia salts. 
