DAMAGE CAUSED BY PLANTS. 79 



results that have in many places been achieved with the cultiva- 

 tion of this species. On the spores germinating, the mycelium 

 enters under the bark wherever it can find any damaged place, 

 resulting from hail, insects, bending of the branches under ice, &c. ; 

 it then penetrates into the woody-tissue and kills the portion 

 attacked, whilst the cankerous spot makes itself outwardly visible 

 by the bursting of the bark and an outflow of turpentine. Small 

 cup-shaped fungi, with bright red receptacles, also appear on the 

 infected places, indicating the cause of the disease. If the 

 cankerous spot be large, and finally extends itself all round the 

 circumference of young trees, the stem dies off above the diseased 

 ring; but when it only extends partially round, the stem may 

 continue alive for decades. 



The wide distribution which this fungus has obtained in low- 

 lying tracts and uplands, in contrast to its much less frequent 

 occurrence, and much less dangerous results, in the true alpine 

 home of the Larch, Hartig thinks can be explained by the 

 fact, that in the damper, stagnating atmosphere of dense forests 

 in close canopy, into which the Larch has been introduced as a 

 subordinate species, the fungi at the infected parts attain a 

 more luxuriant development, and the spores ripen to a greater 

 extent. In the dense forests good opportunities are given to the 

 spores of finding and making use of a germinating bed, whereas in 

 the light, open Larch forests of the Alps, constantly exposed to 

 currents of air, the fruits of the fungus generally dry up with- 

 , out attaining maturity. 



That in damp coombs, hollows, and similar situations, the 

 Larch suffers to a very great extent from the disease caused by 

 this fungus, is well known ; hence the best way to prevent its occur- 

 [ rence will lie in the avoidance of such unsuitable localities, and 

 in growing the Larch in mixed forests, by means of giving it some 

 advantage in growth to start with. 



The Pine fungus (Trametes pini) is much more common in the 



Pine forests of northern than in those of southern Germany, and 



; occurs also, although to a less extent, on Spruce, Larch, and Silver 



I Fir, producing ring-shakes or heart-shakes extending downwards 



I from the crown. It generally occasions rapid decomposition of 



I the timber, owing to the mycelium developing in the wood : it 



betrays its presence in the stem through its brown, woody, mostly 



bracket-like receptacles or spore-producers. The immediate re- 



