234 



WOOD AND FOEEST. 



Nearly all parasitic fungi have two portions, an external fruiting 

 portion which bears the spores — which correspond to the seeds of 

 flowering plants — and an internal portion consisting of a tangle of 

 threads or filaments, which ramify the tissues of the tree and whose 

 function is to absorb nutriment for the fungus. Fungi are classified 

 botanically according to the spore-bearing bodies, their form, color, etc. 

 The parasitic fungi which are especially destructive to wood are 

 those that have naked spores growing on exposed fruiting surfaces 

 (the Hymenomycetes) . In toadstools (the agarics) these exposed 

 surfaces are thin, flat plates called gills. In the polypores, which in- 

 clude the shelf fungi, the spore 

 surfaces are tubes whose open- 

 ings constitute the pores. In 

 the dry-rot, or tear fungus {Me- 

 ruKus lacrymans) , the spore 

 surfaces are shallow cavities. 



Some varieties, called true 

 parasites, develop in uninjured 

 trees, while others, called 

 wound parasites, can penetrate 

 the tissues of trees, only where 

 a cut or injury makes a suit- 

 able lodgment for the spores. 

 Some fungi attack only a sin- 

 gle species of trees, others 

 whole genera; some attack 

 only conifers, others decidu- 

 ous trees, while a few attack 

 trees of nearly all kinds alike. 

 Fungal spores when brought 

 in contact with a wound on a 

 tree or other suitable place, and provided with suitable conditions of 

 growth, germinate, penetrate the tissues and grow very rapidly. 

 These spores send out long threads or filaments which run thru the 

 cells lengthwise and also pierce them in all directions, soon forming 

 a network in the wood called the mycelium. 



Eotting, in a large number of cases, is due to the ravages of 

 fungi. This sometimes shows in the color, as the "red rot" of pine 

 or the '^bluing" of ash. Sometimes as in "pecky" or "peggy" cypress, 



Fig. 80. A "Forest Weed," Floweriuisr Dog- 

 wood. North Carolina. U.S, Forest ~Serz'ice. 



