Homothallism and monosporous mycelia in Coprinus, 201 
made a series of experiments on the fruiting powers of mono- 
sporous and polysporous mycelia of a number of species of 
Coprinus occurring on horse dung at Winnipeg. These copro- 
philous fungi yield an abundance of fruit-bodies spontaneously 
on unsterilised horse dung, can be readily grown in pure culture 
from spores, complete their life-histories in a very few weeks, 
and have black or dark brown spores which stand out con- 
spicuously in agar plates when examined under the low power 
of the microscope. They were thus well suited to serve as 
material for my investigations. Kniep’s papers became available 
six months after the work was begun. 
Until the investigations here described were almost completed, 
I thought, like Mlle Bensaude, that if a monosporous mycelium 
of any species could produce fruit-bodies, evidence was thereby 
obtained which proved that the species is homothallic and not 
heterothallic. However, as soon as Kniep’s IgIg paper came 
into my hands, I perceived that the criterion of fruit-body 
production is insufficient for determining the question of 
homothallism and heterothallism. I have not made any cy- 
totogical studies either of mycelia or fruit-bodies. For deter- 
mining that any species of Coprinus is homothallic and not 
heterothallic, I have relied upon two criteria only: (1) the 
occurrence of clamp-connections upon mycelia of monosporous 
origin, and (2) the occurrence of clamp-connections or com- 
pound mycelia arising from spores all of which have been 
derived from a single fruit-body produced from a mycelium of 
monosporous origin. The value of these two criteria has already 
been discussed. 
Monosporous mycelia have been successfully isolated and 
cultivated for the following nine species: 
Coprinus sterquilinus Fr. C. curtus Kalchb. 
C. lagopus Fr. C. stellatus Buller. 
C. steycovarius Fr. C. cordisporus Gibbs. 
_ C. niveus Fr. C. comatus Fr. 
C. ephemerus Fr. 
The name Coprinus stellatus at present isa nomen nudum. The 
variety of Coprinus ephemerus made use of was purplish in colour. 
This form occurs both in England and Canada. Altogether, for 
the nine species, fifty-six monosporous mycelia were successfully 
transferred to culture media. Of these fifty-six mycelia all except 
three (one of the C. niveus cultures and the two C. comatus 
cultures) produced fruit-body rudiments ; but, as we shall see, 
in many of the cultures, the rudiments never developed into 
mature fruit-bodies shedding spores. 
