200 Transactions British Mycological Society. 
connections are not found in such monosporous mycelia but 
only in compound mycelia formed by the union of two mycelia 
presumably of opposite sex, then one is justified in concluding 
that the species is heterothallic. 
Kniep, when working with Schizophyllum commune which is 
heterothallic, discovered that when a heterothallic species 
produces a fruit-body from a mycelium of monosporous origin, 
not only is the fruit-body haploid but all the spores which it 
produces are of the same sex. Evidence of this fact was obtained 
by sowing the spores of a haploid fruit-body in large numbers 
together in the same culture medium and by observing that 
clamp-connections were never formed in the compound mycelium 
which resulted. The nuclei in the compound mycelium just 
described, therefore, never arranged themselves in the form of 
dicaryons. Assuming these facts to be true, we are provided 
with a second criterion for determining whether a species which 
produces clamp-connections is homothallic or heterothallic. If 
clamp-connections are found in a compound mycelium arising 
from the sowing of numerous spores obtained from a fruit-body 
of monosporous origin, then we are justified in supposing that 
the species is homothallic; but, if no clamp-connections are 
formed, then the species is heterothallic. 
Kniep*, using the clamp-connection criteria, states that he 
has proved experimentally that the following species of Hy- 
menomycetes are heterothallic: 
Polyporus versicolor. 
Typhula erythropus. 
Pentophora corticalis. 
Stereum purpureum. 
Schizophyllum commune. 
Mavasmius alliaceus. 
Armillaria mucida. 
Collybia butyracea. 
C. asema. 
C. tuberosa. 
C. velutipes. 
Mycena calopus. 
M. parabolica. 
Clitocybe infundibuliformis. 
Hypholoma fasciculare. 
H. sublateritium, 
H. capnotides. 
H. Candolleanum. 
H. hydvophilum. 
Pholiota mutabilis. 
P. praecox. 
Coprinus stercovartus. 
He also states that homothallic Hymenomycetes exist and 
cites as examples: 
Hypochnus terrestris. 
Typhula sp.? 
Stereum hirsutum. 
In view of the importance of Mlle Bensaude’s conclusion that 
certain Basidiomycetes are heterothallic, it seemed desirable, if 
possible, to repeat her experiments with a number of different 
species. At the suggestion of Professor Buller, therefore, I have 
* Hans Kniep, Uber morphologische und physiologische Geschlechtsdiffer- 
enzierung, Joc. cit. pp. 12 and 13. This list is given in a foot-note without 
further details. 
