438 PROTECTION AGAINST FUNGI. 



B. Wood and Bark Fungi. 



*4. Trametes Pini, Fr. 

 a. Description and Mode of A Hack. 



The mycelium of this fungus develops in the heart wood of 

 the Scots pine and other trees causing ring-shake. The 

 spring-wood of the annual zones becomes gradually reddish- 

 brown, with numerous regularly distributed perforations 

 coated with white, and at length disappears. The remainder 

 of the wood, and especially the resinous autumn-wood, remains 

 intact for some time, but eventually succumbs so that the tree 



Fig. 211. a Sporophore of Trametes pini, Fr., on the smooth cortex of a 

 Scots pine. 



may become completely hollow. As the mycelium develops 

 most rapidly lengthwise along the infected ring, we find zones 

 of attacked and sound wood alternating. The rotting wood, 

 except in the slightly resinous silver-fir and in spruce 

 branches, is generally bordered by a zone rich in resin which 

 prevents the outward spread of the mycelium. The spores 

 gain admission to the wood through fresh wounds in branches, 

 where green branches have been broken or pruned, and at 

 other wounds. The hyphae destroy the cell walls and pene- 

 trate the heartwood, usually leaving the sapwood unaffected. 



At the scars of dead branches in the case of an infected 

 pine or larch, or anywhere on the bark of a spruce or silver- 

 fir, bracket-like brown sporocarps eventually appear and emit 

 spores which may germinate on fresh wounds, unclosed by 

 resin, on other trees. 



