88 RESEARCHES ON FUNGI 



affright belated wanderers returning home ; but the besom of 

 science has swept away so much superstition that the mycological 

 ghost only afforded an occasion for merriment. 



Armillaria mellea possesses a mycelium which is differentiated 

 into three parts : ( 1 ) a loose branched part which penetrates through 

 wood, etc., and brings about its destruction, (2) a rhizomorpha 

 subcorticalis which occurs in the form of white sheets in or under the 

 bark of a tree, and (3) a rhizomorpha subterranea which occurs as 

 a series of branched and anastomosing, hollow, black, root-like 

 strands, which are often to be found in spaces between loose bark 

 and the wood or growing through the soil away from a tree-stump. 

 Robert Hartig first showed the connection between the rhizomorpha 

 subterranea and the fruit-bodies of Armillaria mellea} Before his 

 investigations the former was believed to be an independent fungus. 

 Hartig discovered that strands of the rhizomorpha subterranea are 

 able to grow through the soil from one root and enter another root 

 by penetrating through the bark and cortex ; ^ and he also found 

 that they not infrequently give rise directly to the fruit-bodies .^ 

 We may therefore consider that the chief functions of the rhizo- 

 morpha subterranea are two : (1) to spread the fungus locally by 

 growing through the soil from one root to another, and (2) to produce 

 fruit-bodies in favourable positions at the surface of the soil. 



According to Robert Hartig, Armillaria mellea is able to kill 

 certain coniferous trees, such as Picea excelsa, and under certain 

 conditions can live as a parasite on woody Dicotyledons such as 

 species of Prunus, Amygdalus, and Acer.* I myself have made an 

 observation in this connection which seems worth recording. In 

 1901, at Sutton Park, near Birmingham, England, there was a large 



^ Robert Hartig, Wichtige Krankheiten der Waldbdume, Berlin, 1874, pp. 22-27. 



2 0. Brefeld (Untersuchungen, Heft III, 1877, pp. 150-151) brought the tips 

 of rhizomorphs grown in pure culture into contact with freshly-dug sound roots 

 of Piyius sylvestris and observed that penetration through the bark took 1-2 days. 

 After penetration, the mycelium grew rapidly under the bark, making its way 

 through the cambial region. 



^ Robert Hartig, loc. cit. 



* Ibid. ; also Robert Hartig, Lehrbuch der Pflanzenkrankheiten, Berlin, 1900, 

 pp. 188-189. W. E. Hiley (3'Ae Fungal Diseases of the Common Larch, Oxford, 

 1919, pp. 144-145) asserts that, in Europe, more trees die from attack by Armillaria 

 mellea than through any other parasitic agent. 



