164 JOURNAL OF THE EOYAL HORTICULTURAL SOCIETY. 



growth and small size of the plants, helps materially. The leaves are 

 often very much reduced as regards area, and their surface is often 

 rolled back upon itself, as in many grasses, heaths, &c. Here also we find 

 the use of the dense covering of hair or felt referred to already, which 

 forms a very effective barrier against the scorching rays of the sun. In 

 the succulent plants we see the most elaborate system of protection 

 against drought. The skin of the leaves and stems forms a very imper- 

 vious coat, inside which a large reserve of water and food is stored up 

 against periods of drought. In the size and brilliancy of the flowers of 

 alpines we may imagine we see the effort of the plants to advertise them- 

 selves during the brief period of their florescence to the comparatively 

 few insects of the mountain solitudes, in order that their blossoms may 

 be properly fertilized, and mature seed result. 



When we come to cultivate alpines and rock-plants in our gardens, we 

 should remember the conditions under which they grow in their native 

 homes. First of all, even in the case of those which live on wet rocks, 

 drainage is perfect ; and that is the sine quel non of a successful alpine 

 garden — drainage, and always drainage. And not only main drainage, in 

 the way of a general draining of the site, should it need it ; but drainage 

 for each plant, in the form of a light porous soil, with ledges and stony 

 pockets. Then we must imitate the sunny and open positions in which 

 they grow in nature, by avoiding overhanging trees or other too dense 

 shade for our plants. The soil should be deep, too, with big blocks of 

 stone, for many of our little alpines have yard-long roots, which they are 

 accustomed to thrust far into the rock crevices, in search of food and 

 moisture. 



Natural rock-gardens of course display a wide variety of conditions. 

 In the Alps or on any similar mountain range a whole series of floras is 

 met with, piled one over the other. Above the limit of cultivation the 

 pine forests climb up the slope, giving shade and a rich humus soil for many 

 very delightful flowers. Above this, sub-alpine bushes often again afford 

 protection. Thence we emerge on the great grassy slopes, gay with a 

 hundred beautiful alpine species— Primulas, Gentians, Soldanellas, and 

 many others ; while around and above are rocky scarps and precipices, the 

 favoured home of innumerable alpines — Saxifrages, Sempervivums, Andro- 

 saces, and so on. 



Arctic plants resemble in many ways those of alpine regions, and it 

 used to be thought that these two peculiar floras were closely allied, and 

 had a common origin. It was held that when the Great Ice Age descended 

 on our earth, and the polar ice-caps crept further and further southward, 

 the polar vegetation w T as pushed southward over the plains before it ; 

 then, when the ice at length retreated, some of the plants migrated again 

 towards the Arctic regions, but others climbed iustead into the mountains, 

 finding there the conditions of cold and exposure to which they were 

 accustomed. But an analysis of the Arctic and the alpine floras shows 

 that as a matter of fact they have little in common as regards composi- 

 tion. Some few species are found in both regions, but the tw T o floras on 

 the whole differ widely. We must look on the alpine flora as a type 

 developed early in mountain regions, which has since, as mountain ranges 

 have slowly arisen and passed away, migrated here and there, so that 



