DASYSCYPHA 283 



disease at such a place are also favoured by the frequent 

 presence of wounds near the surface of the ground. These 

 wounds may be caused by lifting the plants 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 given, the trunks of trees ten or 

 twelve years of age are practically safe against infection 

 except near the top, and there the drier air and exposure to 

 light are safeguards against any serious injury from canker. 



The ascophores vary in size from two to five mm. ; the disc 

 varies in colour from orange to red, externally pure white 

 and minutely downy or hairy under a lens; spores 18-25 X 

 5-6 fJL, paraphyses longer than the asci. The conidial con- 

 dition appears before or along with the ascophores under the 

 form of minute dull yellow pustules ; conidia globose 1*5 ji. 



Much has been written as to the cause and means of 

 prevention of canker. It is perfectly certain, unless our 

 knowledge becomes greatly extended, that the fungus causing 

 larch canker cannot be exterminated. In its native habitats 

 the larch grows at a greater elevation than can be offered it 

 in Great Britain. Under those conditions even, canker is 

 present, but not to an injurious extent. The fungus 

 Dasyscypha calycina is an alien, and was in all probability 

 introduced to this country along with its host, the larch. It 

 is often argued that because splendid woods of larch have 

 been grown in this country, free from disease, and at a very 

 low altitude, that with proper management such conditions 

 could be repeated. This I am afraid is a serious mistake. 

 Such woods were grown by our forefathers, and before the 

 fungus had become generally distributed. Larch would 

 undoubtedly grow in this country just as well as ever it did, 

 but at low altitudes the fungus, now present everywhere, is 

 dominant ; when our forefathers grew their fine larches the 

 fungus had not had time to spread and produce an epidemic. 

 Under the circumstances it is not advisable to plant larch in 

 low-lying, damp situations, and not to plant it anywhere as a 

 pure wood. 



