INJURIES INDUCED BY PLANTS 



211 



may be termed a variety of white-rot. During the progress of 

 the decomposition from the surface of the stem inwards a 

 certain stage is reached, which is highly favourable to the 



FIG. 130. Longitudinal section 

 through the apex of a rhizomorph 

 from the outer hyphse of which 

 numerous hair-like filaments, a #, 

 spring. In the interior the central 

 cells enlarge greatly, b, at a short 

 distance from the apex, while the 

 cells of the hyphse situated to- 

 wards the periphery, c, remain 

 smaller, to form the pseudo-paren- 

 chyma of the "rind" ; d d indi- 

 cates the boundary of the mucila- 

 ginous layer which envelops the 

 strand. ' 



FIG. 131. Transverse section through the 

 cortex and wood of a pine-root which has 

 been killed by a rhizomorph. a, the dead 

 tissues of the bast ; b, the dead cam- 

 im ; c, the medulla of the rhizomorph ; 

 t the pseudo-parenchyma of the rind 

 l "ie rhizomorph ; e e, filamentous 

 which have grown from the 

 rnfzomorph into the wood ; /, dead im- 

 mature wood-cells ; g, a resin-duct which 

 has been completely destroyed, the paren- 

 chymatous cells which surround it being 

 also dissolved. 



development of the mycelium. While previously it was simply 

 filiform and furnished with numerous lateral hyphae, it now 

 develops large bladder-like swellings, and at the same time the 

 hyphae change into a kind of large-meshed parenchyma, which, 

 like the tyloses in the vessels of many dicotyledonous trees, 



P 2 



