28 FOREST TREE DISEASES. 



wood covered by these pioneer hyphae. although some- 

 what discolored and spongy, often appears sound 

 enough to be given full scale. In reality, it has lost a 

 good deal of its strength and generally falls to pieces 

 in drying after having gone through the mill. Tim- 

 ber with this k ' advance rot " should be classed as cull. 

 The classification of white fir by lumbermen as an 

 " inferior species " is very largely due to financial 

 losses arising from handling logs with advance rot. 



The presence of a fruiting body on a dead or dying 

 tree does not necessarily constitute a cause of alarm, as 

 many fungi are not only harmless, but absolutely neces- 

 sary for the economic equilibrium of nature. The pres- 

 ence, however, of any fungus in leaves, needles, or 

 fruits (cones) or of any fruiting body on a living tree 

 is at least suspicious. 



Young fruiting bodies naturally differ very much in 

 aspect from older or dry specimens or ones that may be 

 abnormally developed ; in comparing a fungus found in 

 the field with descriptions or photographs given in this 

 manual, these two points must not be overlooked. 



In nature we find an enormous variety of fruiting 

 bodies. These may appear on needles and twigs in the 

 form of small, round black spots or black lines and on 

 tree trunks, logs, or branches as stools (shelves, conchs. 

 toadstools), or crusts. In different ways they all pro- 

 duce spores (" seed ") in enormous quantities. 



The spores are invisible to the naked eye, are very 

 light, and are carried about by air currents and some- 

 times by insects to other trees. Wherever they find 

 favorable conditions they germinate and start their 



