332 DISEASES OF CULTIVATED PLANTS 



Not much injury is done to the leaves beyond local yellow- 

 spots ; they do not fall before the normal time. When the 

 trunk is attacked the case is different, quite young trees are 

 often killed outright. The mycelium is perennial in the bark, 

 wood, and bast, and extends its area year by year. As a rule 

 the combium is not killed all round the trunk at one point, 

 therefore it continues to grow and produces very eccentric 

 sections, owing to the combium being destroyed on different 

 sides at different levels. Turpentine is secreted in quantity, 

 and escapes through cracks in the bark. As the disease 

 encroaches on the wood, the upward passage of water is 

 checked and the upper branches die, producing the effect 

 known as ' resin-top ' or ' resin-leader.' The aecidia burst 

 through the dead bark late in the spring. Hartig considers 

 that infection of the trunk does not take place after the age 

 of twenty-five years. 



Hartig, Wiehtige Krankh. d. Waldbdumen. 



CALYPTOSPORA (Kuhn) 



Aecidiospores in chains, persistently included in the pseudo- 

 pcridia ; uredospores absent ; teleutospores intracellular, 

 generally longitudinally 3-septate, forming brown spore-beds. 



Cluster cup disease of conifers (Ca/vptospora goepper- 

 tiana, J. Kuhn) possesses two phases in its life-cycle, one of 

 which, the aecidium condition, grows on the leaves of various 

 conifers, Abies peeiina/a (I). C), and on A. nordmannia 

 (Spach.). Infection experiments have proved that the aecidium 

 will also grow on leaves of . lines nobilis (Lindl.), A. magnified 

 (A. Mum), A. coneolor (Lindl.), A. balsamea (Mill.), A.fraseti 

 (Lindl.), ./. cephalonica (Lorn.), A. cilicica (Ant. and Kotschy), 

 A. pictita (Forbes), A.pinsapo (Bois.), and A. victchii (Lindl.). 

 On the other hand, Tsuga canadensis (Carr.) and T. douglasii 

 (Carr.) have resisted all attempts at infection. In conifers the 

 leaves are the part attacked. About a month after infection 

 two rows of white, cylindrical cluster-cups, about half a line 

 in length, appear on the under surface of the leaf; these 

 contain golden yellow spores. 



So far as Europe is concerned the teleutospore stage of the 

 fungus is only met with on the cowberry {Wieeinium vifts- 

 iiiaea, L.) ; it also occurs on V. myrtillus (L.), and V.chandleri 



