296 Studies in Forestry [CHAP. xiu. 



take place when the spores obtain a foothold on wound- 

 surfaces occasioned by insects, hail, &c. ; hence the spread of 

 the disease is greatest in places where the young crops are not 

 vigorous in growth, where insects are likely to be attracted, 

 and where any slight wounds inflicted take longest to heal. 



The first symptoms of the disease are bleaching of the 

 needles, and drying up of the bark and cambium which 

 become brown, more particularly near wounds caused by the 

 caterpillars of the Spruce-bark Tortrix (Grapholitha pactolana). 

 This is followed by the appearance of numerous groups of 

 small red concave peritheda on the bark which contain the 

 tube-spores. Throughout the winter months these are scattered 

 abroad, and spread the disease wherever they happen to land 

 on open wound-surfaces. 



The branching mycelium extends principally throughout the 

 vessels of the new sap-wood and among the intercellular spaces. 

 The whole development of the fungus takes place quickly, 

 although it appears to be accomplished only during the period 

 of rest, and not whilst the cambial layer is in full activity 

 during the summer months. When the disease proceeds round 

 the whole stem, the crown, and often the whole plant, dies off; 

 but, if a strip of bark still remains sound, a cortaceous formation 

 takes place at the edges. This prevents the further spread of 

 the disease ; and after the dead bark of the other part has been 

 shed, the ordinary process of cicatrization begins. 



The only means of combating this disease is to remove 

 and burn, during autumn and the early months of winter, all 

 shoots or young stems attacked. In doing this, care should 

 be taken to remove them in the manner least likely to scatter 

 the spores abroad. 



6. Peziza Willkommii, R. Hartig, the Canker of the Larch. 

 Although a diseased condition of the Larch is caused by bad 

 attacks of the Larch aphis (Chermes /aria's) or the mining moth 

 (Coleophora laricelld), yet the cankerous ailment occasioned 

 primarily by this fungus is widespread and very serious in every 



