Plant Pathology, 



The following interesting article on this subject by Edward John Tilt,, 

 ]\I.D., appeared in a recent number of HardwicMs Science Gossip. — It 

 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 

 repaired mischief; many give evidence to good conservative 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 im- 

 pressions 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 constitu- 

 tional diseases. 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 touchwood, and what 

 relation they bear to each other, of some who are learned in trees, without 

 getting very satisfactory answers, and my ignorance is still unenlightened. 

 To make clear its extent, I will note a few facts, and the inferences 

 suggested to me by my acquaintance with human pathology. 



Touch WOOD. — To grow fine timber, young oaks are left to grow 

 sufficiently near each other to check the free access of air to their lower 

 Iiranches. Their scanty foliage and diminished supply of sap stop 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 beech, the longitudinal half of which had 

 been broken away some years ago. The Avood 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 with this process 

 of disintegrailon, or how is it effected? 



Wet-rot. — During the great wet of last September, 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 J 



