258 Transactions British Mycological Society. 
connections are regularly formed on mycelia of monosporous 
origin, or if clamp-connections are formed on compound mycelia 
arising from spores all of which have been derived from a single 
fruit-body produced from a mycelium of monosporous origin. 
A species of Coprinus producing clamp-connections is hetero- 
thallic if clamp-connections are not formed on mycelia of mono- 
sporous origin but only upon compound mycelia produced by 
the union of two monosporous mycelia presumably of opposite 
Sex. 
Mlle Bensaude, working with Coprinus fimetarius, came to 
the conclusion that, in a heterothallic species, monosporous 
mycelia are always sterile. However, Kniep has discovered that, 
in Schizophyllum commune and certain other species of Hymeno- 
mycetes which are heterothallic, fruit-bodies sometimes appear 
on mycelia of monosporous origin and of haploid nature, one 
nucleus finally entering each basidium instead of two. Fruit- 
body production in a heterothallic species, therefore, is not 
necessarily bound up with the diploid condition of the mycelium ; 
so that if, on experimenting with a new species, one finds that 
a fruit-body is produced on a monosporous mycelium, one is 
not justified by that fact alone in regarding the species as homo- 
thallic. Nevertheless, from my own experience with heterothallic 
strains of Coprinus lagopus and C. niveus, Mlle Bensaude’s 
experience with Coprinus fimetarius, and Kniep’s experience 
with Schizophyllum commune, I am of the opinion that, in a 
heterothallic species, fruiting takes place either not at all or 
much less readily and less perfectly on a monosporous mycelium 
than on a compound mycelium formed by the union of two 
mycelia presumably of opposite sex. 
Ill. METHODs. 
The isolation of mycelia of monosporous origin by plating out 
spores in dung agar was accomplished in the manner already 
described in my first paper. However, owing to the provision 
of a new and improved autoclave, the culture medium was 
sterilised at 15 pounds pressure instead of 7 pounds. 
The pairing of mycelia of monosporous origin in the tests 
for heterothallism was effected as follows. The monosporous 
mycelia were first grown separately upon dung-agar plates or 
in wide test-tubes containing horse dung, and then portions of 
the mycelia were placed in pairs on dung-agar plates. In making 
an inoculation from two plate cultures, a small piece of mycelium- 
covered agar about 7-10 mm. square was removed by means of 
a sterile platinum loop from each of two plates, and.these two 
pieces of agar were placed about 2 cm. apart in the middle of 
a freshly-poured dung-agar plate. In making an inoculation 
