PSALLIOTA CAMPESTRIS 395 



to Mile Bensaude, 1 monosporous cultures of Coprinus fimetarius 

 are quite infertile ; according to Hans Kniep, 2 monosporous cultures 

 of Schizophyllum commune are usually, although not always, in- 

 fertile ; and according to Miss Mounce, 3 in Coprinus lagopus, while 

 fruit-bodies arise on monosporous mycelia, such fruit-bodies often 

 develop very few spores or even no spores at all. In all these 

 heterothallic species, however, fruit-bodies are developed rapidly 

 and perfectly upon secondary mycelia, i.e. mycelia derived from 

 the union of two monosporous mycelia presumably of opposite sex. 

 It thus appears that, in the heterothallic Hymenornycetes, the 

 production of fruit-bodies is largely dependent upon the occurrence 

 of a sexual act taking place between two mycelia presumably of 

 opposite sex. We may therefore ask : Is Psalliota campestris 

 homothallic or heterothallic ? If it is homothallic, then, doubt- 

 less, its fruit-bodies can be produced on mycelia of monosporous 

 origin. If, however, it is heterothallic, then probably one of the 

 conditions for the normal production of its fruit-bodies is the union 

 of two mycelia of opposite sex. No one has attempted to obtain 

 fruit-bodies from Mushroom spawn derived from a single Mush- 

 room spore ; so that, for the present, in respect to Psalliota cam- 

 pestris, we lack knowledge which is vital for a full understanding 

 of the conditions governing fruit-body formation. 



I took some mycelium from a Mushroom bed and examined its 

 hyphae with the microscope. I did not find any clamp-connections 

 either in the independent hyphae or in those making up the mycelial 

 cords. Mile Bensaude 4 and Hans Kniep 5 have shown that the 

 formation of clamp-connections in Coprinus, etc., stands in intimate 

 relation with the conjugate division of a pair of nuclei, so that 



1 Mathilde Bensaude, Recherches sur le cycle evolutif et la sexualite chez les 

 Basidiomyceles, Nemours, 1918, pp. 1-156. 



2 Hans Kniep, " Uber morphologische und physiologische Geschlechtsdifferen- 

 zierung," Verhandl. der Physikal.-med. Gesellschaft zu Wiirzburg, 1919, pp. 8-16. 



3 Irene Mounce, (1) " Homothallisni and the Production of Fruit -bodies by Mono- 

 sporous Mycelia in the Genus Coprinus," Trans. Brit. Myc. Soc., vol. vii. 1921, 

 pp. 198-217 ; (2) " Homothallism and Heterothallism in the Genus Coprinus," 

 ibid., 1922, pp. 256-269. 



4 M. Bensaude, loc. cit. 



5 H. Kniep, " Beitrage zur Kenntnis der Hymenomyceten, III und IV," Zeitschr. 

 f. Botanik, Bd. VII, 1915, and Bd. VIII, 1916. 



