KESTOOKING OS EOCKY MOUKTAINS. 215 



washed down by rain, or been burnt away — as often oc- 

 curs in the Adirondacks — may be covered with materials 

 for producing a forest vegetation. The terraces may 

 also be secured by planting bushes at their outside, 

 thus forming living hedges. These will in due time 

 be covered by the accumulated earthy substances, and 

 then the decaying vegetation will enrich the soil. Upon 

 the soil, which has accumulated between the edges of 

 the terraces, rows of suitable young trees are set along, 

 which, when properly rooted, will secure the object in- 

 tended and prevent the recurrence of further damages 

 by keeping the surface soil from shifting. 



On rocky steeps where there is little or no visible soil, 

 and where seed can only be deposited in chinks and 

 crevices, or sown in occasional patches of soil, seeding 

 will always have the preference to the mode of planting. 

 As for the trees and shrubs to be selected for planting 

 in the fissures and interstices of rocks, there are none 

 which serve the purpose of working through their roots 

 upon the rocks better than the Austrian black pine, the 

 ailanthus, crabapple, and the wild rosebush. In regard 

 to the Austrian pine we have seen in the preceding 

 chapter that it prospers even upon the scantiest and 

 poorest soil, and, therefore, is well qualified for the re- 

 forestation of bare rocks, provided there are some inter- 

 stices or fissures into which it can send its strong roots 

 to retain its holdfast. Of the action of the ailanthus in 

 this respect we can convince ourselves easily by looking 

 at some unfinished rocky parts of our great Central 

 Park. There this tree has obtained such a hold upon 

 the rocks that, after the lapse of another quarter of a 

 century, no artificial means will be required to cover 

 those rocks with vegetation. The crabapple and the 

 wild rosebush make so little demand upon the soil that 

 their seeds, fallen into crevices of old brick walls, sprout, 



