TWO-SPORED BASIDIA 15 



sunlight, future experiments should show that the black spores of 

 Coprini and other Melanospor;e suffer less from prolonged exposure 

 to the sun than the colourless spores of the Leucosporse. 



Two-spored Basidia in Cultivated Varieties of Psalliota cam- 

 pestris. — Atkinson 1 has observed that the basidia of the cultivated 

 forms of Psalliota campestris (the varieties Columbia, Alaska, Bohemia, 

 and others) are two-spored, whereas those of the wild field form are 

 four-spored. However, he found a two-spored variety of Psalliota 

 campestris in the open — once on a lawn, and once on the hillside of 

 a wooded ravine on the campus of Cornell University. My own 

 experience is similar to that of Atkinson. I have noticed that the 

 basidia of the wild form of Psalliota campestris obtained from fields 

 near Birmingham, England, are four-spored, and that those of a 

 cultivated variety on sale in Winnipeg are two-spored. I have also 

 observed a two-spored form occurring on manured ground included 

 within the campus of the University of Manitoba. The campus 

 Mushrooms differed considerably from the wild field Mushrooms of 

 England in that they were more scaly, browner, and possessed rela- 

 tively very shallow gills. Whether or not normal two-spored forms 

 of Psalliota campestris occur in nature as constant types still seems 

 to be a matter of doubt. Atkinson thinks it probable that the 

 cultivated varieties of Psalliota campestris originated as mutations 

 either from Psalliota campestris, or from some other species which 

 has been confounded with it ; and with this view I am inclined to 

 agree. Of two equally well developed Mushrooms, one of which 

 possessed four-spored and the other two-spored basidia, the former 

 would doubtless produce the greater number of spores, and therefore 

 be the more efficient reproductive organ. If this be granted, the 

 two-spored varieties of Psalliota campestris may be regarded as 

 degenerate mutations derived from four-spored ancestors. 



Occasional Sterility of Coprinus Fruit-bodies. — One of the 

 most curious phenomena which has come to my notice in 

 studying the Hymenomycetes, is the occasional sterility of 

 Coprinus fruit-bodies. Strange indeed is the reproductive organ 

 which otherwise undergoes normal development but fails in its 



1 G. F. Atkinson, "The Development of Agaricus campestris,'" The Botanical 

 Gazette, vol. xlii., 1906, pp. 260-261. 



