RED ROT. 675 



properly aerated, or where an impermeable substratum occurs 

 at an inconsiderable depth below the surface of the ground. 

 Wood also readily rots in places where cattle rest at midday, 

 owing to the excrement. 



d. Treatment of Woods. 



A dense condition of a wood, especially in moist or wet locali- 

 ties, favours the evil. Tapping for turpentine, barking by 

 game, and other injuries, such as pruning living branches 

 without tarring, frequently give rise to the first symptoms of 

 red rot in wood, especially when the trees are growing in 

 localities predisposing them to disease. 



3. Causes. 



Widely differing and frequently contradictory hypotheses 

 have been started to explain the origin of red rot. Usually 

 it is attributed to external circumstances, such as unfavourable 

 localities, injuries, etc., without further inquiry into its possible 

 causes. 



The first scientific inquiry into the cause of red rot is found 

 in the works of Willkomm (1866), who designated a microscopic 

 fungus as the sole origin of the disease. He named this fungus 

 Xenedochus ligniperda, and another allied form which springs 

 from it Rhynchomyces violaceus, which causes the bluish colour 

 in rotting wood. 



The question as to the origin of red rot was not by any 

 means solved by Willkomm's researches, as he merely proved 

 the presence of the above fungi in rotten wood, but did not 

 make experiments to infect sound wood by means of their 

 spores, so that it remained doubtful whether the fungi were 

 the causes or merely the consequences of red rot. 



Eobert Hartig, in 1874, solved this question by proving that 

 red rot in the case of spruce, Scots pine, oaks, etc., really arose 

 from infection by parasitic fungi. Later on, in 1877, he further 

 proved that, at least for the spruce, unfavourable soils and 

 external injuries also induced the disease. As we have already 

 in chapter III., part II., discussed the infection of trees by 

 fungi, we have now only to deal with the two latter cases. 



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