Homothallism and Heterothallism in Coprinus. Irene Mounce. 261 
of polysporous origin derived from many spores produced by a 
fruit-body of monosporous origin. I therefore came to the con- 
clusion that C. lagopus is homothallic. There was nothing to 
suggest that this species might be heterothallic. 
After sending my first paper to the press in May 1921, I 
isolated another series of monosporous mycelia of C. lagopus 
and, as I was leaving Winnipeg for Vancouver, took the cultures 
with me. To my great surprise, I found that these mycelia did 
not produce any clamp-connections. During the summer of 
Ig2I, circumstances prevented me from making any further 
experiments; but, on returning to Winnipeg in September, I at 
once began to investigate Coprinus lagopus again with the 
object of solving the problem of the sex of the mycelia in this 
species. 
Altogether, since writing my first paper, I have made 59 new 
monosporous cultures of C. lagopus. Owing to the fact that 
some of the spore-deposits of C. lagopus had been destroyed 
after the completion of my first paper, I was compelled to use 
new spore material. The new spores were provided by ten 
different fruit-bodies. To the best of my knowledge the mycelia 
were isolated in exactly the same manner as formerly. They 
were all transferred to agar plates and, later, 29 of them were 
transferred to sterilised dung in wide test-tubes; and they were 
all kept in pure culture for 50 days and most of them for from 
two to three months. Examination with the microscope yielded 
a result just the opposite of that found in the experiments re- 
corded in my first paper, for not a single one of all the 59 mono- 
sporous mycelia produced any clamp-connections whatever. On 
the other hand, polysporous mycelia derived from several spores 
produced clamp-connections within four or five days after the 
spores were sown. 
These new observations naturally suggested that the strains 
of Coprinus lagopus with which I was working were heterothallic. 
Therefore, assuming that the monosporous mycelia were all 
unisexual and would behave in the same manner as Blakeslee’s 
(+) and (—) strains of Mucor and as Mlle Bensaude’s (+) 
and (—) strains of her Coprinus fimetarius, I paired 23 of the 
mycelia with No. 14 and 7 with No. 46, Nos. 14 and 46 being 
taken as standards. The results of making these 30 pairs are 
shown in Table I. In the fourth column of this table the blanks 
indicate that no observations with regard to fruiting were re- 
corded. 
Of the 30 pairs of mycelia, 17 developed clamp-connections 
in a regular manner, while 13 did not develop any clamp- 
connections whatever. It was therefore supposed that a (+) 
and a (—) sexual strain must have been present in each of the 
