30 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



from the nursery beds, or they may be formed by the feet or 

 the tools of the workmen during planting. Where trees are 

 planted by 'notching,' the turf is firmed round the base by the 

 repeated application of the heel of the planter, and in doing so 

 it not infrequently happens that the boot comes in contact with 

 the stem and abrades the bark. And should the plant escape 

 injury during planting, it is still very likely to be injured near 

 the ground by rabbits, hares, voles, and other animals." 



For the reasons already stated, the trunks of trees over ten 

 years of age are practically safe against attack from canker, 

 except near the apex, and there the drier air does not favour the 

 earliest stage of inoculation so much as the damper conditions 

 that prevail near the ground. If the trunk escapes the disease, 

 canker attacking the branches at a later stage does not, as a rule, 

 interfere with the continued growth and development of the tree. 



The cup or ascophore varies considerably in size, ranging from 

 two to five millimetres, externally snow-white, and minutely 

 hairy under a pocket-lens ; the disc varies from deep orange to 

 red. The cup is not distinctly stalked, but is somewhat 

 narrowed at the point of attachment The spores are variable 

 in size, ranging from 18-25 x 6-8 /x; paraphyses longer than the 

 asci (Fig. 2, PI. II.). 



The characttristic appearance of canker caused by the fungus 

 is sufficiently familiar to most of those interested in the subject 

 as to require no detailed description. Fig. 1, PI. I., shows a 

 typical canker of small dimensions, with the fungus — ascophores 

 and conidia pustules — natural size. 



The mycelium of the fungus is most abundant in the cortex 

 and cambium region, but it also enters the wood (Fig. 26, 

 PI. III.). 



In the great majority of instances, canker commences on a 

 very young stem or branch, in the axil of a dwarf shoot, which 

 was presumably occupied by an aphis "foundress," as already 

 described. Again, when canker is present on a thick trunk or 

 branch, there are almost invariably the remains of a dead branch 

 in the centre of the canker depression. In the axil of the dead 

 branch, which had been partly cracked away from its origin by 

 snow or wind, the spores of the fungus first found an entrance 

 into the then living tissues. 



In addition to the larch and Scots pine, I have also succeeded 

 in producing canker by artificial inoculation on branches of the 



