DUROCHER ON SOILS AND VEGETATION. 37 



the other hand, the secondary hmestones form very level plateaux, 

 with extremely little wood ; and the trees too are of a different kind ; 

 the oak and chestnut, which abound in the fields in the ancient for- 

 mations, being replaced by the elm. A similar change may be ob- 

 served in the small limestone basins which occur in Brittany and on 

 parts of the coast. In the same manner as the elm, the maple {Acer 

 campestre) and the walnut are more developed on the calcareous soil ; 

 the birch, the willow, the oak, and the chestnut thrive better on the 

 argillaceous and siliceous formations. The maritime pine is cultivated 

 with success on the same soils, even in the most interior localities ; 

 the beech appears to prefer the granitic soils. The furze {Ulex euro- 

 pceus) and broom {Sarothamnus scoparius) grow spontaneously, or 

 are cultivated on the older formations, but not on the limestone soils. 

 The colza (colewort) and tobacco flourish in some parts of the littoral 

 region, and the lucerne also succeeds there. In like manner, as on 

 the calcareous soils in the interior, the peat-mosses in the west occur 

 principally in its low lands. 



Among the plants growing spontaneously, few can be cited as ex- 

 clusively characteristic of the schists, the sandstones, or the granites, 

 though many are found on one soil rather than on another. The vege- 

 tation of the argillaceous or siliceous tertiary deposits also offers few 

 peculiarities when compared with that of the primary or transition 

 formations. The most striking contrast is between the flora of the 

 calcareous soils and those soils which do not contain lime in notable 

 quantity ; but these differences are becoming less sensible, as calca- 

 reous substances are more generally applied to improve the soil. A 

 certain number of plants are found both in the maritime region and on 

 the few, small, calcareous deposits occurring in Brittany, but rarely 

 or almost never on other formations : among these are Linum angusti- 

 folium, Silene injiata, S. ffallica, S. otites, S. conica, Reseda lufea, 

 Asperula cynanchia. Ononis repens^ Anthyllis vulneraria, Poterium 

 sanguisorba, Eryngium campestre, Scabiosa arvensis, Anchiisa italicay 

 Linaria minor, L. supina. Salvia verbenaca, Erigeron acre, Thesium 

 humifusum, Chlora perfoliata. Iris foetidissima, &c. Certain plants 

 which differ from the former in appearing not to suit the maritime 

 region, grow exclusively on calcareous soils, or are more frequent 

 there than in other places. Such are the Orchis pyramidalis, O. 

 hircina, Ophrys apifera, Op. aranifera, Lepidium campestre, Thlaspi 

 perfoliatum, Diplotaxis muralis, Dianthus carthusianoriim, Litho- 

 spermum officinale, Helianthemum vulgare, Astragalus glycyphyllos, 

 Medicago marginata, M. Gerardi, Hippocrepis comosa, Scabiosa 

 columbaria, Stachys germanica, S. annua, Galeopsis ladanum, Cala- 

 mintha acinos, Melampyrum cristatum, Cichorium inthybus, Cen- 

 taurea scabiosa, and many other species. In general the soils cover- 

 ing the tertiary or Jurassic limestones appeared to present a greater 

 number of characteristic plants than the soils lying on the palaeozoic 

 limestones or on the marbles, undoubtedly because the latter being 

 less friable have yielded less detritus to the vegetable soil. 



The influence of the limestone formations shows itself even on 

 animal life. It manifests itself in the development of freshwater and 

 terrestrial shells. So also the crabs abound in many of the rivulets 



