Homothallism and monosporous mycelia in Coprinus. 205 
two ahead of the first monosporous cultures and sometimes a 
day or two later. There was nothing to show that a polysporous 
culture has any more vigour than a monosporous culture. 
Although it appears that Coprinus sterquilinus is undoubtedly 
homothallic and that it is perfectly vigorous when its nuclei 
become paired as a result presumably of hyphal fusions taking 
place between branches of the same mycelium; yet, under 
natural conditions, crossing is by no means excluded and 
probably often takes place. When several spores germinate 
together, as they must often do in horse-dung in fields, the 
mycelia doubtless soon anastomose. Thus the condition is 
provided, even in a homothallic species, for the first dicaryon 
to arise by a nucleus of one mycelium moving across a bridging 
hypha to another mycelium and thus pairing with one of the 
latter’s nuclei. An analogy is provided by certain hermaphrodite 
Flowering Plants in which either self-pollination or cross- 
pollination may take place. 
IV. CoOPRINUS LAGOPUS. 
Coprinus lagopus, which was the second species studied, comes 
up very commonly on unsterilised horse-dung cultures in both 
Europe and North America. The fruit-bodies obtained at 
Winnipeg fit the description of C. lagopus as given in Lange’s 
monograph on the genus Coprinus*, and they also correspond in 
detail with the illustrations of C. lagopus as given by Brefeld7. 
Ten monosporous mycelia and one bisporous mycelium of 
Coprinus lagopus were isolated from dung-agar plates, trans- 
ferred individually to dung-agar slants, and finally transferred 
to wide tubes containing sterilised horse-dung. Within fourteen 
days from the time the spores were plated out from the spore- 
deposit, the mycelia on the eleven agar slants all showed 
rudimentary fruit-bodies; and, subsequently, in nine out of the 
ten monosporous cultures as well as in the bisporous culture, 
some of the fruit-bodies expanded. The bisporous mycelium 
produced a fruit-body one day after the monosporous ones, but 
otherwise behaved precisely as they did. The monosporous dung 
cultures varied somewhat in the length of time they took to 
develop. Transferring the mycelium to the dung seemed to 
check the growth of some of them temporarily. Seven of them 
produced rudimentary fruit-bodies seven days after transference 
to dung, one nine days after, one ten days after, and the last 
sixteen days after transference. The bisporous mycelium de- 
* Jacob E. Lange, Studies in the Agarics of Denmark, Dansk Botanisk 
Arkiv, Bd. 11, Copenhagen, 1915, p. 41. 
t O. Brefeld, Untersuchungen, Leipzig, Heft 111, 1877, Taf. vi, fig. 1, a-g. 
