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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



watered' by the melting snows and with the least possible amount of 

 humus. It is among these plants that the horticulturist finds the 

 species whose culture costs him his greatest efforts. The conditions 

 under which they grow in their native haunts are so abnormal when 

 compared with those obtaining in lowiand gardens that the difficulty 

 experienced in their cultivation is scarcely a matter of surprise. 



Before leaving the subject of the physical conditions of the alpine 

 soil in all its variety the rock-plants proper must receive a passing 

 notice. Nothing can be more instructive than to study the plant life 

 growing on some isolated boulder lying in the middle of an alpine pas- 

 ture. In its cracks and hollows a certain amount of humus will have 

 collected. On the shady side, more especially if wet, Pinguicula alpina, 

 Saxifraga Androsace, S. aspera, and S. controversa are among the likely 

 finds. On the sunny side Campanula pusilla, Saxifraga Aizoon, 

 Sedums, Sempervivum arachnoideum and *S'. montanum, Androsace 

 helvetica, Draha aizoides, Globularia cordifolia, and, in the Pyrenees, 

 Saxifraga longifolia may be taken as representative plants. The study 

 of the vegetation on these boulders is one of the most useful object- 

 lessons which the Alps afford. Nothing more forcibly illustrates 

 how a slight variation in the amount of humus, aspect, and humidity 

 will at once produce a corresponding variation in the type of vegetation. 



Most cultivators are aware that attempts have been made at a three- 

 fold division of alpine plants according to the chemical composition of 

 the substratum in which they flourish. This division has taken the 

 following form. Firstly, plants which thrive on a soil rich in lime 

 or ' calcicole ' plants. Secondly, plants to which lime is injurious or 

 ' calcifuge ' plants, and, lastly, plants which in this respect are indif- 

 ferent in the matter of soil. Unfortunately, for the enthusiasts for ex- 

 haustive classification, further investigation has shown the matter to be 

 far less simple than they originally supposed. One of the very first 

 authorities on the subject, the French botanist, Professor Gaston 

 Bonnier, has made a special study of this question. He prepared lists 

 of calcicole and calcifuge plants in several different districts — for the 

 French Alps, in Dauphin^, for the Austrian Alps, and for the Car- 

 pathians — with the result that he found that plants which in some dis- 

 tricts were calcicole, in other districts might be distinctly calcifuge and 

 vice versa, and he also found that plants which in one district exhibited 

 a distinct preference for either calcareous soil, or siliceous soil, in other 

 districts were indifferent in the matter of soil. To give but one of many 

 instances. The Edelweiss proved calcifuge in Dauphine, indifferent in 

 the matter of soil in Austria, and calcicole in the Carpathians. Very 

 few, indeed, were the instances of plants which in all districts alike were ' 

 uniformly either calcicole or calcifuge. This, I think, conclusively 

 shows that the influence of the presence, or absence, of lime in the soil { 

 upon plants is at most local, and depends upon external conditions , 

 which vary with the district. It, therefore, by no means follows that | 

 a plant which requires one kind of soil in the Alps will exhibit a similar I 

 preference in our English gardens. Profound as is the influence of the 



