198 Transactions British Mycological Society. 
HOMOTHALLISM AND THE PRODUCTION OF 
FRUIT-BODIES BY MONOSPOROUS MYCELIA 
IN THE GENUS COPRINUS. 
With Plates VI and VII. 
By Miss Irene Mounce, M.A. (British Columbia). 
I. INTRODUCTION. 
In a publication entitled ‘‘ Recherches sur le cycle évolutif et 
la sexualité chez les Basidiomycétes’’ Mlle M. Bensaude* records 
the results of certain experiments and cytological observations 
which appear to show that Coprinus fimetarius—one of the 
Basidiomycetes—resembles certain Mucorini investigated by 
Blakeslee in that it is heterothallic. 
In making cultures of Coprinus fimetarius in Van Tieghem 
cells, Mlle Bensaude obtained four mycelia, each of which had 
originated from a single spore. These four monosporous mycelia 
were transferred to tubes, but only two of them survived this 
change of conditions and continued to grow. The two surviving 
monosporous mycelia, a and f, were sub-cultured; but during 
eight months they remained in the primary condition, 7.e. none 
of them developed clamp-connections or paired nuclei, and they 
all proved quite sterile, for none of them produced any fruit- 
bodies. On the other hand, the behaviour of a mycelium of 
polysporous origin was quite different. Mlle Bensaude obtained 
polysporous mycelia by mixing pieces of the mycelia of my- 
celium @ and mycelium f. She found that, as a result of hyphal 
fusions taking place between a and f, a mycelium was produced 
which was definitely secondary in nature, for its nuclei were 
paired and divided conjugately, the division of each dicaryon 
was accompanied by the formation of a septum with a clamp- 
connection, and the mycelium as a whole was fertile, as was 
shown by the production of fruit-bodies. 
Mlle Bensaude’s criteria for determining heterothallism in her 
fungus were: (1) the isolated condition of the nuclei and the 
absence of clamp-connections in monosporous mycelia, (2) the 
formation of dicaryons and clamp-connections when two 
different mycelia, a and £, were brought together so that they 
might anastomose with one another, and (3) the sterility of 
* Mathilde Bensaude, Recherches sur le cycle évolutif et la sexualité chez 
les Basidiomycétes, Nemours, 1918, pp. 1-156, nine plates. 
