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On Diseases of Plum Trees 



Lateral penetration of the hyphae takes place through the pits 

 which abound in the tissues of the wood (cf. Fig. 7). This penetration 

 is very slow, and often limited to the young wood, e.g. in a dead branch 

 8 ins. in diameter, from a Prince of Wales tree, hyphae could be found 

 in the outermost § ins., and in the inner part of this zone only in the 

 medullary rays. In the vessels themselves the hyphae were limited 

 to the outermost \ inch. 



The cell walls are practically unaffected by these fungi, sections 

 from a large dead branch failing to show any discoloration after 

 prolonged treatment with Schultz's reagent; in consequence dead 

 wood, although brittle, shows no signs of crumbling. 



Fig. 6. 



The formation of pycnidia is preceded by an aggregation of hyphae 

 in the tissues of the bark to a small hard pustule, which gradually 

 enlarges, splitting the bark in the process. Owing to the friability of 

 diseased bark, this process could not be followed in detail. 



In "Victoria (3)," the hyphae are dark coloured, large, fairly thick 

 walled, and stain with difficulty; in the remainder, they are thin 

 walled, narrow, hyaline, and stain readily. With this single exception, 

 the above description applies to all the specimens examined. 



Culture experiments and characters of the fungi in 

 pure culture. 



All attempts to bring about maturation of the asci in the only 

 perithecium found having failed, the description which follows applies 

 entirely to cultures obtained from conidia. 



Separate experiments in regard to the germination of spores were 

 made with all the "strains" mentioned above, and there was complete 

 agreement in the results attained. 



