458 



BASIDIOMYCETES. 



point, whereby a felted tissue, called the medulla, is produced 

 in the interior. The outer parts of the pseudoparenchyma, on 

 the other hand, coalesce to form the so-called rind, which when 

 young gives off numerous delicate hyphae, and these, taking 

 advantage of the medullary rays, penetrate the wood, and 

 especially the resin-ducts, should such be present. In the wood 

 the growth is upwards. This filamentous mycelium, which pro- 

 gresses much more rapidly in the interior of the wood than 

 the rhizomorphs which grow in the cortex, completely destroys 



FIG. 288. Agui'ii'us 'meld us. Rhizomorphs in the form of dark anastomosing 

 bands, developed between the bark and wood of a tree. (v. Tubeuf phot.) 



the parenchyma that exists in the neighbourhood of the resin- 

 ducts, and to all appearance this is accompanied by a partial 

 conversion of the cell-contents and the cell- walls into turpentine. 

 The turpentine sinks down under its own weight, and in the 

 collar, where the cortex is withered, having been killed by 

 rhizomorphs, it streams outward, pouring partly in between the 

 wood and the cortex, and partly into the surrounding soil at 

 places where the cortex has ruptured owing to drying. On 

 this account the disease was formerly called ' Uesin-nux ' or 



