CHAP. XVII INFLUENCE OF CHEMICAL CONDITIONS OF SOIL 67 



Partial to a certain soil, are those that show a preference for it without 

 however being strictly confined to it. 



Restricted to a certain soil, are those Umited to it. 

 In accordance with this we can distinguish : calcicolous plants, 

 silicicolous plants, slate-plants, halophilous plants, and so forth.^ 



Of other botanists who likewise assume that the chemical constitu- 

 tion of soil has a controlhng influence, we may mention, among Germans, 

 Sendtner, Schnitzlein, Niigeli ; and among Frenchmen, Vallot, Fliche, 

 Grandeau, Saint-Lager, Contejean (in later years), Magnin. Upon the 

 whole, French investigators appear, in recent times, mainly to support 

 this view. 



Various facts favour this interpretation. On p. 58 it was pointed 

 out that certain substances in excess act on certain plants as poisons. 

 This is seen most clearly in the case of common salt. 



Halophilous plants. Halophytes are not only of highly characteristic 

 morphological and anatomical architecture, but have an absolutely 

 defined topographical distinction on coasts, and in salt deserts and salt 

 steppes. Common salt in excess has a highly exclusive action ; it acts 

 as sterihzer, and only relatively few species, mainly belonging to 

 definite families (Chenopodiaceae, and others), can endure much of it. 

 Section VII should be consulted for further particulars in reference to 

 halophytes. 



Calciphobous plants. In cases of other substances, lime for instance, 

 the matter is more doubtful. Lime is essential to the plant. Certain 

 plants are stated to avoid soil containing much calcium carbonate.^ 

 Such reputedly calciphobous species are : Castaneasativa, Pinus maritima, 

 Calluna vulgaris, species of Erica, Sarothamnus scoparius. Genista anglica, 

 Ulex europaeus, Pteris aquilina, Rumex Acetosella, and other plants that 

 we often find on heaths and on raw humus ; also Gramineae, Cyperaceae, 

 many lichens and mosses, especially Sphagnum,^ and among algae the 

 Desmidiaceae. The flowering plants named are reputed to be incapable 

 of carrying on an existence in soil containing more than from 0-02 or 0-03 

 per cent, of calcium carbonate. But cultures made by C. A. Weber * 

 and Grabner have clearly demonstrated that none of these plants suffer 

 from lime when this is unaccompanied by a large amount of soluble 

 salts. 



Calciphilous plants. Other plants that do not desert a soil rich in 

 calcium carbonate are put forward as calciphilous plants, for example : 

 Papihonaceae (Trifohum, Anthylhs, Vulneraria, Ononis Natrix, and others), 

 Rosaceae, Labiatae, many Orchidaceae, Tussilago Farfara, and others. 

 Unger gives a whole array of examples belonging to the hme-flora. Accord- 

 ing to Blytt^, Ophrys muscifera and Libanotis montana are the sole 

 vascular plants in Norway that occur exclusively on calcareous soil. 

 Among algae the Mesocarpaceae are calciphilous. 



Silicicolous plants. These are brought forward in contrast to calci- 

 colous plants. The calciphobous plants mentioned above are regarded 

 as silicicolous. The truth may perhaps be that they are expelled from 



' See Chapter XV, pp. 56-8. ' See p. 58. 



* Fliche et Grandeau, 1888 ; sec Contejean, 1893. 



* C. A. Weber, 1900. ' BIytt, 1893. 



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