AS A NUCSE-PLANT TO OAK. v383 



trees may gradually be obtained. These are not mere collar- 

 shoots, such as spring from the base of the common alder, but 

 true offsets, rising at the distance of some feet from the parent 

 plant And if the latter be cut down to make way for an oak or 

 other principal tree beside it, the young under-growth is ready 

 to form a bush of rods resembling those of hazel, where it stood. 



But the silver alder, in its native countries of Sweden, Eastern 

 Germany, the Carpathians, and the Tyrol, is by no means con- 

 fined to humid or heavy soils. In the Tyrol, where I have 

 examined its distribution and habitats, over a great extent of 

 hill-sides, valleys, and flat mountain pasturages (as also in the 

 Canton of Uri in Switzerland), it often covers vast knolls and 

 hill-flanks of ancient gravel and sand, now lifted up by subter- 

 ranean forces far out of the reach of the existing rivers. Its 

 power of propagation by offsets, as well as by seed, enables it to 

 cover the surface closely with a coppice very like that of hazel, 

 and to keep both parching sun and withering frost from the 

 ground. Nevertheless, it prefers the coldest and bleakest parts 

 of the valley-heads, running up as high as the birch would do 

 towards the snow-line. At last it is replaced by alnus mridis, 

 the green or unhoary elder, which closely resembles it however 

 in foliage, but approximates in flower and fructification to the 

 birch, and is a mere low shrub. This last runs up to the snow- 

 line itself after thus replacing alnus ineana, just as the dwarf 

 birch, betula nana^ replaces on our own mountains the common 

 birch near the summits. 



Having observed the valuable properties of alnus incana, and 

 above all its habit of throwing up offsets, about twenty-five 

 years ago I began to insert the species, wherever I had a vacancy, 

 in my own plantations in Northumberland, near the Cheviots. 

 It grew with remarkable vigour, making always long shoots the 

 second summer after being planted. No frost affects it, for its 

 wood is ripened in autumn, earlier a good deal than the shoots of 

 the common alder. Nor does the coldest spring do it any harm. 

 It comes into leaf with the birch, and is intermediate in general 

 appearance between the birch and the common alder, having a 

 graceful foliage, hoary on the under side, and a shining bark of 

 metallic gloss like that of the young mountain ash. 



No tree stands up better to the west wind, and it shares with 

 the common alder the properties which make both such excellent 

 neighbours to the oak, namely, that it rarely exceeds twenty -five 

 feet in height, and, instead of losing its under branches, like the 

 birch, retains them well. 



In the closer parts of the woodland it forms poles of a very 

 useful kind, and of equable thickness, well adapted for making 

 light rails for laying across weak places in hedges, or similar 

 purposes. I know of no tree comparable to it as a nurse for oak 



