262 TIMBER AND SOME OF ITS DISEASES, [chap. 



Much more disastrous results can be traced directly 

 to the action of the mycelium in the cortex. The 

 hyphse grow and branch between the green cells of 

 the true cortex, as well as in the bast-tissues beneath, 

 and even make their way into the medullary rays 

 and resin-canals in the woods, though not very deep. 

 Short branches of the hyph^ pierce the cells, and 

 consume their starch and other contents, causing a 

 large outflow of resin, which soaks into the wood or 

 exudes from the bark. It is probable that this 

 effusion of turpentine into the tissues of the wood 

 cambium, and cortex, has much to do with the drying 

 up of the parts above the attacked portion of the 

 stem: the tissues shrivel up and die, the turpentine in 

 the canals slowly sinking down into the injured 

 region. The drying up would of course occur in any 

 case if the conducting portions are steeped in turpen- 

 tine, which prevents the conduction of water from 

 below. 



The mycelium lives for years in the cortex, and may 

 be found killing the young tissues just formed from 

 the cambium during the early summer: of course the 

 annual ring of wood, &c., is here impoverished. If 

 the mycelium is confined to one side of the stem, 

 a flat or depressed spreading wound arises ; if this 

 extends all round, the parts above must die, 



