lOO 



THE FACTORS [Part ] 



of plants, their absence from a substratum rich in lime is quite compre- 

 hensible. It is not less intelligible that many species, although not special!) 

 requiring lime, are restricted to a calcareous soil. As with the halophyte; 

 in relation to sodium chloride, it is the fugitives from the struggle fo: 

 existence which, on a silicious soil, are unable to maintain themselve; 

 against stronger competitors, but endure a calcareous soil better than they. 



That the peculiar character of the flora of calcareous soil depends ii 

 the first place on its chemical properties would never have been doubtec 

 if the same species of plants always behaved in the same manner ; this, how 

 ever, is only to a limited extent the case. Only those species to which lim 

 is poisonous are always absent from a calcareous soil ; as regards othe 

 species, the difference between a lime-flora and a siliea-flora is not constan, 

 as it is betzvecn halophytes and 7ion-Iialophytes, but varies with the locality 

 In a region with several kinds of soil, but with the conditions determinin 

 the existence of vegetation otherwise the same throughout, there ar 

 always certain species of plants found only on calcareous soil, and other 

 only on silicious soil, whilst a third group is more or less indifferent. List 

 of the three groups in any particular district will be only partially valid i 

 a second district. Many a calciphobous species of the first district is calc: 

 philous in the second, or the reverse, and many species that in one district ar 

 selective in the matter of soil appear in another district on any kind of soi 



Bonnier, for instance, found that the lists which had been drawn u 

 for the Swiss Alps, of plants more or less confined to a certain kind ( 

 soil, were no longer completely valid in Dauphinc. Much less do the}' hoi 

 good for the Carpathian mountains or for Scandinavia. Thus the larch i 

 Switzerland and the Tyrol prefers the most primitive rocks, which are poc 

 in lime, and is seldom found on limestone ; whilst in Bavaria and Salzbur 

 it is quite commonly found on calcareous but not on silicious soil ; again, i| 

 the Carpathian mountains it grows on all kinds of soil indifferently. 



Literature presents a fairly large number of similar cases : ' Pinus montana. Mil 

 in its varieties uncinata and Pumilio, is a decidedly calcicolous plant ; there [in tl 

 Swiss Alps] it alternates, markedly according to the substratum, with Alnus viridij 

 The mountain pine produces its dwarf forests on the rubbly slopes of the limestor 

 rocks, whilst the alder clothes the declivities of the primitive rocks. In the Carp 

 thians, on the contrary, the mountain pine is indifferent as to the soil' (Chris 

 The following species are, according to Wahlenberg, confined to calcareous soil , 

 the Carpathians, but are indifferent in Switzerland, according to Christ: Dry; 

 octopetala, Saxifraga oppositifolia, most of the alpine Leguminosae, Gentiai 

 nivahs, G. tenella, G. verna. Erica carnea, Chamaeorchis alpina, Carex capillar! 

 Eupleurum stellatum, and Phaca alpina, are confined to calcareous soil in tl 

 Carpathians, but prefer sihcious soil in Switzerland. Geum reptans, accordii 

 to Bonnier, grows in Savoy (Mont Blanc) exclusively on calcareous soils, in Dauphii 

 exclusively on silicious soils ; in Switzerland it appears to be indifferent. 



