THE HONEY FUNGUS 151 



They were described by Jos. Schmitz, whose account with 

 some additions was included by de Bary in the first edition 

 of his MorpJiologie der Pilze (1866), and at that time several 

 different fungi which grew as parasites on the rhizomorphs 

 were regarded as their fructifications by various authors. 



It was not until 1874 that Hartig discovered that both 

 forms of rhizomorphs are mycelial growths of the fungus 

 Armillaria mellea, or as it was then called Agaricus melleus. 

 Brefeld in 1877 obtained rhizomorphs in pure cultures 

 grown from spores of the fungus, and thereby confirmed 

 the association. The following account is derived chiefly 

 from de Bary, Hartig, and Brefeld, who worked out the 

 development and morphology of the rhizomorphs in great 

 detail. 



It will be best to begin with the germination of the spores. 

 These germinate in a nutrient solution in a few days, though 

 germination does not take place in pure water. On a decoc- 

 tion of plums they produce circular masses of white mycelium 

 which grow slowly, reaching a diameter of little more than 

 5 cm. in about eight days, and then stop. Next, closely- 

 woven masses of hyphae appear near the centre, which are 

 at first light in colour, but later dark brown. These dense 

 clumps of mycelium resemble the sclerotia (hard mycelial 

 growths which function as perennating organs) of many 

 fungi, and we may follow Brefeld in regarding the rhizo- 

 morphs as sclerotia which have developed growing points 

 by which unlimited extension and branching are rendered 

 possible. 



Of a number of such sclerotium-like bodies only one or 

 two develop into rhizomorphs ; the rest cease to grow and 

 become covered with white hyphae. The growing points only 

 become operative on the lower side of the sclerotia, not on 

 the upper side where they lie free of the culture substratum. 

 Once growing points are formed the rhizomorphs quickly 

 grow parallel to the bottom of the dish, and only cease to 

 lengthen when the nutrient material is used up. By remov- 

 ing them to a fresh decoction Brefeld obtained renewed 

 growth and profuse adventitious branching, and by further 



