FOREST PATHOLOGY. 



By EDWARD JOHN TILT, M.D. 



T is difficult to get out of 

 a groove, and the habit 

 of looking at mankind 

 as either healthy or 

 diseased sticks fast to 

 me, when riding about 

 the Windsor woods 

 and forests, and I am 

 always on the look-out 

 for patients among the 

 trees. Trees resemble 

 human creatures : the strongest bear traces of re- 

 paired mischief; many give evidence to good con- 

 servative surgery, in the shape of well-formed stumps 

 •and the healing-over of extensive wounds ; but many 

 trees get wounds that cannot be healed by nature, 

 and constitutional diseases that are fatal. Riding 

 the woods reminded me of my first impressions when 

 walking the hospitals as a raw medical student. It 

 then seemed to me that I could understand surgical 

 cases, but it was like looking into a bottle of ink to 

 attempt to understand fevers and constitutional dis- 

 eases. In the woods I am quite at home with forest 

 surgery, and quite at sea with the constitutional 

 diseases of trees. 



I have asked, — what is dry-rot, wet-rot, and touch- 

 wood, and what relation they bear to each other, of 

 some who are learned in trees, without getting very 

 satisfactory answers, and I fall back on the learned 

 correspondents of SciENCE-GossiP to enlighten my 

 ignorance. To make clear its extent, I will note a 

 few facts, and the inferences suggested to me by my 

 acquaintance with human pathology. 



Touchwood. — To grow fine timber, young oaks 

 •are left to grow sufficiently near each other to check 

 the free access of air to their lower branches. Their 

 scanty foliage and diminished supply of sap stops 

 their growth, they become brittle, lose their moisture, 

 and turn to touchwood. Windsor Forest is thus 

 strewn with the lower branches of oaks planted in 

 1820. I have picked out great lumps of touchwood 

 from the trunk of a large and still vigorous columnar 

 No. 145. 



beech, the longitudinal half of which had been broken 

 away some years ago. The wood near the bark 

 was quite sound, but the central part of the wood, 

 deprived of sap and exposed to the air, had become 

 touchwood. Has a fungus anything to do 7uith this 

 process of disintegration, or how is it effected ? 



Wet-rot. — During the great wet of last Sep- 

 tember, and in a very wet hollow of the Forest, I 

 one day found that a well-grown oak, about 400 

 years old, had snapped across at about three feet 

 from the ground ; and the freshness of the foliage, as 

 well as the cleanness of the wound, showed the 

 smash to be very recent. It was a fine case, with 

 bold splinters of sound wood, for the tree was for 

 the most part healthy ; but it was easy to see, that as 

 the sound wood approached the point of fracture it 

 was simply wet, then it became soaked with wet. 

 Nearer to the seat of mischief this soddened wood 

 could be easily broken up with the fingers, and 

 showed that a fungus was at work between its rings. 

 In a hollow, where the tree had snapped, could be 

 seen how actively this fungus was doing its work ; for 

 I could tear out large masses of a yellowish-white- 

 looking, sweet-smelling, spongy, elastic substance 

 reeking with wet, in which the concentric rings could 

 still be traced, separated by a white soft pith-like 

 fungoid growth. This tree had some years before 

 been seriously damaged near the point of fracture, for 

 there was a dark-coloured flesh-wound, and a hole in 

 this wood was lined by dry-rot, to a very limited 

 extent. I believe that in this case the dry-rot only 

 acted as a wood-perforator to flood with water the 

 central parts of the tree, and I never met with an- 

 other case in which dry-rot was associated with wet- 

 rot. Mr. Menzies, the highly-accomplished Deputy 

 Surveyor of Her Majesty's Woods and Forests, looks 

 upon wet-rot as a purely local disease, to be cured by 

 scooping out of the tree all its diseased wood, and by 

 preventing the access of water. I showed a bit of 

 the spongy substance just described to a country 

 gentleman, and he told me it would turn to touch- 

 wood when dry ; but it is now tough and semi-elastic. 



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