go 



Aside from tlic direct injury of the stones carried down with the mass- 

 es of earth, the chief destruction Hes essentially in the covering of the parts 

 of the plants which hitherto had been exposed to the free air. Many plants, 

 however, die if they are permanently planted too deep and only those can 

 withstand being covered with soil which possess the ability of readily strik- 

 ing adventitious roots. Among herbacous plants the grasses growing on 

 dunes should be emphasized especially as having this quality (Arundo 

 arenaria L., Elymus arenarius L., etc.) ; our quack grass (Agropyrum re pens 

 P. B.) also easily works its way out through a heavy covering. Among 

 trees, the willows and poplars withstand such a covering without great dis- 

 advantage, and especially the (Seekreuzdorn) (Hippophae' rhamnoides L.), 

 which grows on gravel and sand, is found on the coasts of Germany, France 

 and England, and serves, with its flat lying roots, as a means of retaining 

 the dunes. In opposition to this, the bases of the trunks of many trees, as 

 for example, fruit trees, are very sensitive to deep, lTea\y soil covering. 

 Also in transplanting trees, or in grading, a change in level covers the base 

 of the trunk, which has been exposed to the air, leads to a weakening and 

 shows phenomena of disease which will be treated of more in detail. In 

 potted plants the Ericas are most sensitive to the smothering of too deep 

 planting. It must be assumed that the cause of death is a lack of oxygen 

 for the roots which have been set too deep and covered by large amounts of 

 earth. 



Landslides, besides covering the lower lands, expose the roots ; 

 which fact deserves attention. So long as the forest remains intact, 

 interwoven roots form a network with such small meshes that the soil is 

 held firm. If, however, holes are torn in this by the h.and of man or by 

 storms, so that the plants are uprooted, then the soil begins to push down 

 from the higher places and in fact the m^ore quickly, as the soil is more 

 broken and the wind finds the more access to the torn places. Aside from 

 processes of this kind which take place unceasingly in high mountains and 

 before which we usually stand powerless, changes in the forests, even on 

 the plains, take place constantly as a result of the exposure of the roots from 

 the working away of the soil. This is especially the case in forests in hilly 

 places when streets are cut through. The forest soil is usually porous or 

 becomes so by drying and as soon as the street cuts through a hill over- 

 grown with large trees, the free roots are found at the edge of the cut, from 

 between which the soil has fallen out or been worked away. The injury is 

 two-fold since the exposed side of the root crown weakens the anchorage of 

 the trees and the decreased supply of water impairs the formation of the 

 tree top. 



The statement that the injury caused by such cutting of the forest for 

 shortening the road is compensated for by the increased growth of trees is 

 an error. To be sure this may, under certain circumstances, effect a con- 

 siderable increment of growth, as, for example, Hartig's^ investigations 



1 Havtig, Ueber den Lichtstandszuwachs der Kiefer. Allg. Forst- u. Jagdzei- 

 tung. LXIV, 1888, Januar. 



