2 RESEARCHES ON FUNGI 



species, make possible the co-operation of more or less numerous 

 monosporous mycelia in the formation of one or more fruit-bodies. 1 

 Since Volume IV was written, the author has realised that there 

 are two other special functions associated with hyphal fusions : 

 (1), in Arthrobotrys oligospora, the formation of numerous mycelial 

 loops which function in the trapping and killing of the larvae of 

 Nematode worms 2 ; and (2), in Pyronema confluens and other 

 Discomycetes, the repair of wounds made by the killing of one or 

 more cells in the series of cells making up a long hypha. The repair 

 of these wounds will be treated of in Chapter II. 



Hyphal fusions occur not only in the mycelia but also in the 

 fruit-bodies of the Higher Fungi, e.g. in the very young fruit-body 

 rudiments of Pleurage anserina and in the pileus-flesh of Marasmius 

 oreades. In the larger fruit-bodies of the Hymenomycetes. the 

 hyphal fusions which there develop no doubt : (1) aid the flow of 

 nutrient substances to the growing hyphae and spores during fruit- 

 body development ; (2) connect the living hyphae together so that 

 these may the more readily serve as a unit in the development of a 

 fruit-body as a whole ; and (3) increase the mechanical stability of 

 the fruit-body flesh. 



The pileus-flesh of Marasmius oreades and of many other species 

 of Agaricaceae is made up of a three-dimensional network of lwphae 

 in which, collectively, the air-spaces between the hyphae are much 

 greater in volume than the hyphae themselves. If one cuts through 

 the pileus of a Fairy-Ring fungus and looks at the cut surface, one 

 sees that it is white. This whiteness, like that of snow and of white 

 petals, is due indirectly to the presence of air-spaces between the 

 units of structure — here the hyphae. If one places a drop of water 

 on the cut surface of the pileus, the water is at once absorbed : 

 by capillarity it is drawn into the spaces between the hyphae. 

 Notwithstanding its great porosity, the pileus-flesh of M . oreades is 

 decidedly tough. This toughness is due in large measure to the 

 existence of numerous hyphal fusions between adjacent hyphae, 

 which fusions during their formation served to convert the hyphae 

 as a whole into a fine-meshed coherent tissue. 



1 These Researches, Vol. IV, 1931, pp. 181-184. 



2 Cf. \Y. Zopf, Die Pilze, Breslau, 1890, pp. 17-18. 



