60 JOUENAL OF THE EOYAL HORTICULTUEAL SOCIETY. 
than the Swiss Alps we find that the evidence is conflicting. M. Bonnier * 
has emphasised this fact by comparing the distribution of alpine species 
in regard to soil in the Alps of Dauphiny, Austria, and the Carpathians. 
He finds that a number of species which are entirely confined to 
calcareous rocks in one district are indifferent as to the nature of the soil 
in another. For instance, Calamintha alpina, L., grows chiefly on sandy 
soils in the Alps of Dauphiny, on calcareous rocks in the Austrian Alps, 
but is indifferent as to soil in the Carpathians. He concludes that the 
chemical nature of the soil has a certain influence on the distribution of 
some alpine species, but only relatively, not absolutely. 
The chemical character of the soil al(.ne is therefore insufticient to 
explain such instances of distribution. We must look more especially to 
the other factors connected with soils for an explanation of the significance 
of such phenomena. The pliijaical properties of the soil, its permeability 
to water, and its power of retaining water, vary very largely in different 
geological formations, and exert a powerful influence on the distribution 
of plants. The need of a rich humus (i.e. decomposing organic material) 
is essential to the welfare of many plants, as are also the fungal elements 
known as Mycorhiza, which live in symbiotic association on the roots of 
some species, and by whose aid the absorption of organic material by the 
plant is promoted. All these factors have to be taken into account as 
well as the chemical nature of the soil, and until we know more of the 
requirements of each alpine species in these respects it will not be 
possible to explain the precise significance of the distribution of certain 
alpines, such as those above mentioned. 
Another interesting feature of the Swiss flora is the replacement of a 
lowland plant by another nearly related species at high elevations. The 
common Daisy, Bellis perennis, L., is not found within the alpine zone, 
but is there replaced by Bellidiastrum Michel ii, Cass., the Alpine Daisy. 
Another instance is that of Banunculus montanus, AYild., which in Alpnie 
meadows replaces Banunculus acris, L. 
The extreme beauty of alpine flowers, both in respect to form and 
colour, is too well known to require more than a word in passing. The 
colours of most alpine species are very intense, and it has been shown by 
M. Bonnier t and others that the intensity of colouration increases with 
the altitude. This is especially marked in such species as Campanula 
rotundifolia, L., and Myosotis sylvatica, Hoffm., in which there is a con- 
siderable difference in the colour of the corolla between the lowland and 
alpine forms. The number of blue and violet flowers is also much 
greater in proportion in alpine than in lowland plants. Many alpine 
species of Gentians, Primulas, Veronicas, Pol} galas. Campanulas, &c., 
have an intensely blue colour, while other alpine genera, such as Saxi- 
fraga. Anemone, Phyteuma, and many others, have one or more species 
with bluish flowers. The massing or clumping together of many 
individuals of the same species is another natural feature of alpines, 
especially in high Alpine regions. It is due to this, in combination with 
their bright colours, that alpines are rendered so conspicuous — an adap- 
tation connected with cross-fertilisation. 
* Bonnier, M. G., Ann. cle Sci. Nat., Otli Series, vol. x. 18S0. 
f Bonnier, M. G., JiulL cle la Soc. Hot. de Fiance, 1880. 
