R J. Tabor and Kate Barratt 21 



It is obvious that pollards are particularly exposed to the attack 

 of parasites which can obtain an entrance and destroy the heart wood, 

 and these old beeches are in most cases nothing but hollow shells. 

 The outer wall of wood and bark has also suffered frequently from 

 accidental injury and disease, and is now a patchwork of dead and living 

 tissue. In fact it is astonishing to observe in some instances, how 

 restricted is the tract of living, conducting tissue, which connects a 

 well-developed limb above with the root system below. It must 

 operate as a limiting factor in the relations between the root system 

 and the leafy canopy dependent upon it above ; and it is a fact that 

 the trees are extremely sensitive to anything which tends to disturb 

 these relations, e.g., dry seasons, clearing and felling in the immediate 

 neighbourhood. For the same reason they demand constant attention 

 in the matter of pruning, mulching, etc. It is obvious that any attack 

 on these vital tracts must raj^idly prove fatal, and they are particularly 

 exposed to the ravages of facultative parasites which have established 

 themselves on the neighbouring areas of dead tissues. Moreover 

 diseases affecting the bark are much more rapidly fatal than those 

 attacking the wood, since the death of the inner bark and with it the 

 cambium, deprives the tree not only of the means for conveying its 

 elaborated food materials, but of its capacity for forming new tissues. 

 A number of fungi are found constantly growing on the pollards, and 

 amongst others Fomes fomentarius, Stereum hirsutum, S. purpureum, 

 Armillaria niucida, etc. 



The Ranger, Mr M. C. Duchesne, observed that fruit bodies of 

 Bidgaria pok/morpha, Wett., were often abundant on trees exhibiting 

 the gumming. The evidence of association however between the 

 fungus and the disease was not at all convincing. 



At the time our attention was first called to the disease the fruit 

 bodies of the fungus were scarce. Trees showing the gumming often 

 exhibited no trace of Bulgaria, whilst on the other hand felled logs, 

 with the bark covered with the scars and remains of old fruit bodies, 

 usually showed no evidence of gumming. It was possible moreover 

 that the disease might have no connection with a parasite, but have 

 resulted from some functional disturbance. Our attention was therefore 

 directed not only towards the examination of the diseased bark for 

 evidence of the presence of any living organisms which might be con- 

 cerned with the disease, but also to determining whether the disease 

 could be transmitted to healthy trees. 



