CHAP. XTII.] Fungoid Diseases of Trees 291 



at branch -holes of the trees attacked, or else direct out of the 

 bark, where it forms a brown, woody, bracket-like receptacle 

 or hymenium ; and the spores scattered from this infect other 

 wound-surfaces, unless these are protected by resinous outflow, 

 or by having been tarred after any pruning of the Scots Pine. 

 The technical value of Pine stems often becomes much reduced 

 owing to this disease. It often happens that these spore- 

 producers live for a long time (up to fifty years, according to 

 R. Hartig l ) and gradually assume large dimensions. 



The immediate removal of trees attacked by the fungus 

 appears advisable, not only in order to be able to utilize the 

 timber before decomposition has proceeded too far, but also 

 in order to prevent the spread of the disease by the scattering 

 of the spores produced in immense numbers in the receptacle. 

 The removal of Scots Pine branches in which heart-wood has 

 already begun to form should be avoided ; or, if pruned, then 

 the wound-surfaces should be coated over with tar. 



2. Aeddium pini, Pers., var. corticola, the Pine Canker or 

 Bark-fungus. 



This is a disease to which Pines in general, and Scots Pine 

 in particular, are liable both as poles and trees, but principally 

 as young poles about fifteen to twenty years of age. The fungus 

 appears first on portions of the tree that are of at least two 

 years' growth, mostly at the whorls, and near the top of the 

 tree. 



Some kind of wound in the bark is necessary before the 

 spores of this fungus can effect an entrance ; but when once 

 this has been gained, the presence of the disease is first noticeable 

 by the appearance of small bright semi-spherical or oval orange- 

 reddish pustules (aetidia) protruding from the' bark of branches 

 and stems in June, which swell up and burst, scattering the 

 spores they contain. The colourless, septated hyphae of the 

 fungus live intercellularly between the parenchym cells of the 

 bark, the liber, and the medullary rays, and send haustoria or 

 1 Op. dt., p. 164. 

 u 2 



