HEART-ROT CAUSED BY OTHER FUNGI 131 



of all degrees of thickness from Gfj. downward, but some of 

 the largest, in the earlier stages of rot, have brown contents. 

 • These thicker, browTi hyphae generally run either vertically 

 along the tracheides, or horizontally, boring through the 

 tracheide walls and markedly constricted in the bore-holes. 

 The finer hyphae, which are much more numerous, branch 

 frequently and spread in all directions, though the bore- 

 holes are nearly always transverse to the tracheide walls. 

 Hyphae may also grow up between 

 the tracheides. As decomposition 

 proceeds fewer hyphae are found, 

 but even in advanced stages of rot 

 a few colom'less hyphae are gener- 

 ally present. The same variation 

 in size and colour of the hyphae 

 is also a feature of the felted my- 

 celium which fills up the cracks 

 in the rotted wood. 



Although the mycelium in the 

 wood lacks those special features 

 of interest which characterize the 



growth of Fomes annosus and t. ^o ^r i- 

 ° Fig. 53. — Mycelium 



Armillana 7nellea, the effects pro- Polyporns SchweinitzU 



duced in the wood are pecuHar and ^}^ '''?°^ °* t^•' l^^^^'i = ^>-^ 



^ hyphal bore - hole ; h.h., 



distinctive. In the nrst place the brown hypha ; h.p., bor- 



wood is never quite deUgnified, ^^'^'^^ pi* 5 ^■^■' colourless 

 and to the last will give a slight 



reaction with phloroglucol and hydrochloric acid. At the 

 same time the cellulose, which, though present in normal 

 wood, fails to give normal reactions without special treat- 

 ment, is so far freed from hgnone that rotted wood gives 

 a blue or purplish colour with chlor-zinc-iodine. Thus 

 the presence of Hgnone and the presence of cellulose may 

 be demonstrated, without special treatment, in the same 

 cell wall. Dm-ing the process of decomposition the wood 

 also undergoes contraction to a very marked extent. In 

 the final stages this is apparent to the naked eye by the 

 large cracks and crevices, but before these appear evidences 



K i 



of 

 in 



