Homothallism and Heterothallism in Coprinus. Irene Mounce. 265 
obtained by setting out portions of the mycelia in plates by 
themselves. In none of these sub-cultures were clamp-connec- 
tions ever produced. 
Since, as indicated in Table I, Nos. 23, 25, 26, 27 and 29 all 
produced clamp-connections with No. 14, it was to be expected 
on the strict (+) and (—) theory of sex that they would all 
behave uniformly with respect to other mycelia; but, by looking 
along the horizontal rows in Table III, it will be at once seen 
that this expectation was not justified by experience. Thus 
although with No. 21 they all gave clamp-connections, yet with 
Nos. 22, 23 and 25 they did not all behave uniformly; for with 
No. 22 they all produced clamp-connections except No. 25, 
with No. 23 they none of them produced clamp-connections 
except No. 26, and with No. 25 they none of them produced 
clamp-connections except No. 29. 
The results given in Table III are identical in their nature 
with those obtained by Hans Kniep with Schizophyllum 
commune*, 
VII. CoPpRINUS* NIVEUS. 
In the series of experiments upon Coprinus niveus recorded 
in my first paper, I found that clamp-connections developed: 
(I) on each of several mycelia of monosporous origin derived 
from the spores of a wild fruit-body, (2) on each of two mono- 
sporous mycelia derived from spores produced by a fruit-body 
of monosporous origin, and (3) on a compound mycelium of 
polysporous origin derived from many spores produced by a 
fruit-body of monosporous origin. I therefore came to the con- 
clusion that Coprinus niveus is homothallic. 
In the winter of 1921-22, I made a new series of experiments 
which yielded results quite different from those previously ob- 
tained. The source of the spores was a wild fruit-body which 
came up spontaneously on horse dung in the laboratory. 
Nine monosporous mycelia were isolated and transferred to 
dung-agar plates and afterwards sub-cultured in other plates; 
but, even after the lapse of 32 days, they all failed to produce 
clamp-connections. On the other hand, a compound mycelium 
of polysporous origin derived from many spores produced clamp 
connections in abundance ten days after inoculation. 
The presence of clamp-connections on the mycelium of poly- 
sporous origin and their absence from the nine mycelia of 
monosporous origin at once suggested that my new strain of 
Coprinus niveus was heterothallic. A complete series of crossings 
with the nine mycelia was therefore undertaken. The results 
are shown in Table IV. As before, the numbers above and to 
* H. Kniep, loc. cit. p. 12. 
