CLITOCYBE ROOT ROT OF WOODY PLANTS 11 



morphic (rootlike) in character, are commonly produced in cultures 

 of the fungus. An additional feature of the mycelial sheets is the 

 frequent occurrence of a peculiar perforate character, clearly apparent 

 (figs. 5 and 6). This appears to be a character of diagnostic value 

 for G. tabescens and one which apparently is not found in A. mellea. 

 Freshly dug roots that show mycelial sheets under the bark are char- 

 acterized by a pronounced mushroom or fungus odor. 



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Figure 6.— Part of mycelial sheet developed between bark and wood of root of 

 sand pine killed by Clitocybe root rot, showing perforate character and sug- 

 gestion of radial growth. X5. 



The black, rounded or flattened cortical or subterranean shoestring- 

 like rhizomorphs so frequently accompanying the closely related root 

 rot fungus A. mellea have not been observed to occur in the case of G. 

 tabescens. However, a peculiar development of blackish, hardened, 

 sometimes frilly, mycelial extrusions, similar to those reported for 

 A. mellea, frequently occur on the bark of roots attacked by C. ta- 

 bescens. These structures originate as outgrowths of the mycelial 

 sheets or xylostromata developed between the wood and the bark, 

 becoming extruded through longitudinal fissures in the bark (fig. 7). 



An additional symptom of Clitocybe root rot is the occasional de- 

 velopment of clusters of the mushroom fruiting bodies of the fungus 



