OTHER HYMENOMYCETES 171 



limited food-supply may have been a factor tending to increase 

 the number of hyphal fusions. When the drawing was made, 

 very few freely-ending hyphae, such as the one shown at e, could 

 be found. The union of a diploid myceHum with a haploid mycelium 

 of C. lagopus is shown in the next chapter in Fig. 135. The union 

 of two diploid mycelia of Panus stypticus is illustrated in Volume III, 

 Fig. 176 (p. 415). Falck,! in his extended study of the destruction 

 of wood by species of Lenzites observed that in Lenzites hyphal 

 anastomoses are characteristic both of the primary myceUum — 

 which he calls the netzmycel — and of the secondary myceUum ; and, 

 in an illustration of the myceHum of Lenzites abietina present in 

 the tracheides and medullary-ray cells of Abies alba, he represents 

 the hyphae as being joined into a network. Doubtless, under 

 natural conditions, many spores of oiie and the same hymeno- 

 mycetous species often settle close together on the same organic 

 substratum, such as wood, dead leaves, etc., and germinate side by 

 side. Wherever this happens, it is probable that the monosporous 

 mycelia join together to form a single compound net-mycelium 

 which acts as a unit in the formation of one or more fruit-bodies. 

 There is therefore good reason to suppose that social organisation, 

 like that described in Coprinus sterquilinus, is characteristic of the 

 Hymenomycetes in general. 



Recent studies on sex in the Hymenomycetes indicate that most 

 Hymenomycetes are heterothaUic, i.e. that two monosporous 

 myceUa of opposite sex must unite and their nuclei become con- 

 jugate, before a normal diploid fruit-body can be developed. Among 

 these heterothaUic species may be mentioned : Coprinus lagopus,^ 

 Panaeolus campanulatus ,^ Collybia velutipes,^ Marasmius oreades^ 

 Schizophyllum commune,^ and Fomes pinicola."^ In view of our 

 knowledge of social organisation in the Hymenomycetes, we may 

 be sure that, under natural conditions, single fruit-bodies of these 

 and other heterothaUic Hymenomycetes are not always the product 

 merely of the two mycelia of opposite sex from which their nuclei 



1 R. Falck, " Die Lenzites-Faule des Coniferenholzes," in Holler's Haus- 

 schwammforschungen, Jena, Heft III, 1909, pp. 102, 104, Taf. V, Fig. 4. 



2 Irene Mounce (1921). » R. Vandendries (1923). 



* F. Zattler (1924). ^ In my own laboratory, hitherto unpublished. 



« H. Kniep (1920). ' Irene Mounce (1926). 



