Homothallism and Heterothallism in Coprinus. Irene Mounce. 267 
So far as concerns Coprinus lagopus and C. niveus, the results 
of my two investigations are discordant ; for, in the first, mono- 
sporous mycelia gave rise regularly to clamp-connections whilst, 
in the second (described in this paper), clamp-connections never 
appeared in monosporous mycelia (59 isolations for C. lagopus 
and g for C. miveus) but only after the pairing of two mono- 
sporous mycelia presumably of opposite sex. My first investi- 
gation therefore led me to believe that Coprinus lagopus and 
C. mveus are homothallic, whereas my second one has provided 
conclusive evidence that there are strains of both these fungi 
which are heterothallic. 
It may be asked: admitting that all the new observations go 
to show that Coprinus lagopus and C. miveus are heterothallic, 
how is it that different results pointing to homothallism were 
obtained in the first investigation? There appear to be two 
alternative explanations: (1) in my first investigation some error 
crept into the work, (2) there are homothallic strains of both 
these fungi as well as heterothallic. 
I have not been able to think of a single source of error in 
my first work that could account for the results obtained. So 
far as I know, I used the same method for isolating and culti- 
vating the mycelia for my second investigation as for my first. 
I do not think that the plates became infected by spores from 
the air, or that I confused species or spore-deposits; and | 
certainly saw the clamp-connections described, for I sketched 
some of them with the camera-lucida. If I made some mistake 
in method, I must have repeated it quite consistently in every 
one of my first experiments, for all the results were consistent, 
all the monosporous mycelia having produced clamp-connec- 
tions, and I must have avoided this error consistently in my 
second experiments, for no clamp-connections ever made their 
appearance in the 68 new monosporous cultures. On the other 
hand, it is to be remembered that my first investigation was 
chiefly devoted to the fruiting of monosporous mycelia, that 
the question of the presence or absence of clamp-connections 
was taken up only toward its conclusion, and that the number 
of observations was relatively few. It is also noteworthy that 
in my second series of experiments with Coprinus lagopus, 
although I used ten different fruit-bodies, I was unable to 
obtain any more homothallic strains, and therefore at no time 
have I been able to grow simultaneously homothallic and 
heterothallic strains of this fungus. 
Blakeslee* found that, in the heterothallic Mucors, each 
monosporous mycelium is either (+) or (—), and that in these 
* A. F. Blakeslee, Sexual Dimorphism in Cunninghamella, Botanical 
Gazette, LXXII, 1921, p. 186. 
