Chap. V] THE SOIL 99 



in relation to this the smaller amount of chlorophyll that is present in the 

 leaves on the calcareous soil, we may with probability conclude that in 

 calciphobous plants, when they grow on calcareous soil, the absorption of 

 iron or its transport through the plant is prejudiced, and tJius the formation 

 of chlorophyll is checked. Contejean has also observed that the colouring 

 of Sarothamnus, Ulex, Calluna, Anthoxanthum Puellii is always yellowish 

 when they grow under such conditions. 



The physiological causes of the injurious influence of calcium carbonate on 

 certain species of plants are rendered more comprehensible by the researches 

 of Fliche and Grandeau ; but, on the other hand, the difference in the be- 

 haviour of different species remains quite unexplained. An affinity on the 

 part of calciphilous plants for carbonate of lime, similar to that of halo- 

 phytes for sodium chloride and of nitrophytes for saltpetre, does not appear 

 to be here in question ; the quantities of lime absorbed from the same soil 

 by the different species of plants are indeed as a rule very unequal, but 

 without any perceptible connexion with a greater or less capability the 

 plants may possess of thriving on a substratum that is rich in lime. 



In the planted forest of Champfetu, on soil poor in lime (0-35 °/ o CaO), 

 there are found growing together the calciphilous Cytisus Laburnum 

 with 27*15 °/ o CaO in its ash, the calciphobous Ulex europaeus with 

 25-97 °/ o CaO, the calciphobous Sarothamnus scoparius with 25-03 °/ o CaO, 

 and the indifferent Robinia Pseud-acacia with 58-97 °/ o CaO. If we 

 consider that the laburnum contains only half the quantity of ash contained 

 by the other species it follows that although it is calciphilous it is poorer 

 in lime than its calciphobous allies. 



ii. CHARACTER OF THE FLORA ON CALCAREOUS SOLL. 



The flora of a district the superficial soil of which results, in some parts, 

 from rocks poor in lime, such as granite, sandstone or slate, and, in other 

 parts, from rocks rich in lime, exhibits, in the flora of the two kinds of soil, 

 a contrast that at once strikes the eye, although many plants occupy 

 both the soil rich in lime as well as that poor in lime. Of plants in 

 Central Europe strictly confined to a soil poor in lime are, for instance, 

 Calluna vulgaris, Vaccinium Myrtillus, Sarothamnus scoparius, Scleranthus 

 perennis, Rumex Acetosella, Digitalis purpurea : similarly, of species found 

 only on calcareous soil there are Prunus Mahaleb, Aster Amellus, Hippo- 

 crepis comosa, Teucrium montanum, T. botrys, Globularia vulgaris, Epi- 

 pactis rubiginosa. Many species show merely a decided preference for 

 the one or the other kind of soil, without confining themselves to it so 

 strictly. Thus the common bracken is rarely seen on calcareous soil, 

 Anthyllis Vulneraria and Scilla bifolia rarely on soil poor in lime — a soil 

 being considered poor in lime that contains less than 3 °/ o . 



Owing to the injurious influence of carbonate of lime on certain species 



H 2 



