234 DISEASE IN PLANTS. 



saprophytes, but their activity is concerned with 

 the putrefactive processes going on in the diseased 

 wood, and which may lead to rotting of the 

 timber. 



The origin of the wounds in the bark and 

 cortex, and which extend into the wood and other 

 tissues as the putrefactive and fermentative pro- 

 cesses increase, appears to be in some cases at 

 least due to lightning. 



Resin-flux or Resinosis. The stems of Pines 

 and other conifers are apt to exude resin from any 

 cut or wound made by insects, or by the gnawing 

 of other animals ; but in many cases the flow is 

 due to fungi, e.g. Perideriniuni, the hyphae of 

 which invade the medullary rays and resin canals 

 and thus open the way to an outflow through 

 cracks in the bark. Agariais melleiis not only 

 invades the resin passages, but stimulates the tree 

 to produce abnormal quantities of resin, which 

 flows down to the collar and roots, and exudes 

 in great abundance at the surface of the soil. 

 Various other plants also exude resin from 

 wounds, ^nd in some cases the flux seems to be 

 increased by degeneration of the tissues, e.g. 

 Copaifera. 



Gummosis. Cherries, Apricots, Acacias, and 

 many other trees are apt to produce abnormal 

 quantities of gum, which flows from any wound or 

 exudes through cracks in the bark. Degeneration 

 of the wood-cells, and especially of the cell-walls 

 of a soft wood formed by abnormal activity of the 

 cambium, points to its origin being due, in some 



