Fungus Diseases 43 



known to the uninitiated long after the mischief has been 

 done. 



On the roots, besides the rot fungi, there are found others 

 which attack the hving parts and hence become directly a 

 damage to the life function of the tree. 



While here too, as a rule, an injury or weakened condition 

 invites the fungus attack, there are fungi which appear to 

 attack perfectly healthy and uninjured roots. Thus the 

 southern root rot which infests a large number of tree species, 

 kills the roots so extensi\'ely as to produce a sudden wilting 

 of the leaves and subsequent death of the tree. Poorly 

 drained and poorly aerated soils seem to favor its develop- 

 ment. 



The honey mushroom also kills young trees and weakens 

 or stunts the growth of older trees which finally, if a dry, 

 hot season occurs, may dry up for lack of water-supply. 

 Its mycelium grows not only in, but alongside the roots 

 through the ground, within a few inches of the surface and 

 thus spreads from tree to tree, increasing the area infested. 



Some few plants other than fungi may be found as para- 

 sites on branches and bole; they are mischievous, although 

 rarely of importance unless extraordinarily de\'eloped. 

 Among these are \'arious species of mistletoe, which occa- 

 sion objectionable burl-like malformations, due merely to 

 the mechanical obstructions to the wood growth which their 

 roots, imbedded in the cambium layer of the host, produce. 

 The dying of the branch above this burl may be the con- 

 sequence. The trouble is spread by the seeds of the mistle- 

 toe, which are covered with a sticky substance and are 

 carried by birds to other branches and trees; hence its spread, 

 at least, can be prevented by removing the affected branches. 



In addition to the parasitic fungi and other parasitic 

 plants, there will be found on all trees epiphytes, i.e., 



