Chap. II] REGIONS OF VEGETATION 715 



assimilated more vigorously, and in the light gave off more aqueous vapour, but in 

 darkness gave off less, than those of lower stations. The proportions of the fresh 

 and dry weights were not determined ; there were also no data regarding the meta- 

 bolic processes of the alpine experimental plants at alpine heights. The knowledge 

 acquired could not be applied to the latter. 



It may be confidently regarded as established that alpine altitudes promote the 

 production of sugar in the nectaries of flowers. Thus, according to Bonnier and 

 Flahault ', the flowers of Silene inflata, Isatis tinctoria, Euphrasia officinalis, Leonto- 

 don autumnalis, growing between 1,500 and 1,800 m. above sea-level— an altitude at 

 which the effects of mountain climate are not yet very marked— are richer in nectar 

 than they are in plants growing between 200 and 500 m. Hermann Miiller found the 

 spur of Platanthera bifolia in the lowlands at the most one-third full of nectar, but 

 in the Alps often much more than half full. 



Interesting in this connexion is a communication by Layens 2 , regarding the 

 statistics of bee-keeping in the Departement des Pyrenees Orientales, according to 

 which the department possesses 19,829 hives which are tolerably uniformly distri- 

 buted between sea-level and 1,500 m. altitude, and which, grouped according to 

 zones of altitudes of 300 m. each, give the following average yield : 



Altitude in m. 



0-300 



300-600 



600 -900 



900-1200 



1 200- 1 500 



The aroma of plants, that is to say the amount of ethereal oils they contain, is also 

 supposed to increase with the altitude. Bonnier has in fact proved that there was 

 an increase of reservoirs of resin and oil in his alpine cultures. The aromatic scent 

 of alpine hay has often been referred to, and rightly so. Yet the phenomenon does 

 not appear to be universal. Thus, the flora of the treeless region of Java does not 

 contain one single plant with aromatic flowers, although these are very common in 

 the lowlands, and it has only a few with aromatic vegetative parts, like Gaultheria 

 and Gnaphalium. The fruits of alpine species of Rubus and Vaccinium, apart from 

 their small amount of acid contents, are utterly tasteless, and the same is true of 

 European fruit-trees, for instance plum, cultivated in the upper part of the montane 

 region, whereas tropical fruits in the lowlands possess the most intense aroma. 



Many features of alpine plants, according to the experiments and 

 observations described above, appear to be direct effects of the alpine 

 climate, but they have become more or less hereditary, and our know- 

 ledge of the components of the alpine climate enables us, in many cases, 

 to recognize their individual causes. As to other phenomena we can 

 indeed appreciate the uses they subserve ; but it is not at present possible 

 to decide whether they likewise were directly induced by the climate, 

 or were the result of the natural selection of accidental variations. Thus, 



1 Bonnier et Flahault, op. cit., p. 93. 2 Layens, op. cit., p. 206. 



