136 HEART-ROT CAUSED BY OTHER FUNGI 



One form causes a ' dry rot ' on structural timber not 

 unlike that produced bj' the dreaded Merulius lacrymans. 

 Both occur in houses, especially in cellars and other damp 

 or ill- ventilated situations, and rot the woodwork to such 

 an extent that it collapses under any strain that may be 

 put upon it. Sm-faces of the rotting wood are often covered 

 by a thickish layer of felty mycelium traversed by veins of 

 denser conducting hj^phae. Such layers are made by 

 Merulius lacrymans as well as Porta vaporaria, but with 

 increasing age the two fungi may be readily distinguished 

 by the fact that with Merulius the}' become grey and silky 





Fig. 55. — Poria vaporaria : a, li^phsi, sliowiiig buckle connexions ; 

 a, early stage allowing how the connexion grows out from one side of the 

 septum ; //. laler .stage, in which the wall hetwecii the connexions and the 

 part of the hypha on the other side of the sej)tuin has been absorbed. 

 B, hyphal bore- hole ; c, in section ; d, in surface view. 



on tlie surface, whereas Avith Poria they remain white antl 

 felt-like. Tliese mycelial layers are very like those found 

 in the open on trees attacked by Poria. But the humid 

 conditions and large area of wood surface afforded by the 

 under-side of an ill- ventilated floor, or similar situation in 

 a bnilding, allow of ;i much more massive mycelium than 

 is generally found in the forest. 



I'oJyporiis sulphurcus. Fr. We now come to two fungi 

 which, thougl) they cause iieart-rot in the laich, are definitely 

 woimd j);uasiteK, and iufcci llie ti"ee through sub-aerial 

 wounds oi' deafl Iwancli snags left l)y the fall of the larger 

 branches. These two fungi are Pohiporus siiljihureus and 

 Traiaeles Pini. 



Neither of these fungi has yet provtul very destructive 

 to the larch in Britain, and with the former, at awy rate, 

 little fear need be entertained as to its power for evil in 

 well-regulated woods. The sulphur ])olypore has been 

 fountl in li^uroxie on oak, locust {Robinia pseudacacia) , 



