Homothallism and Heterothallism in Coprinus. Irene Mounce. 263 
develop clamp-connections, gave rise only to imperfect fruit- 
bodies. These varied from about the size of a pin’s head to 
rudiments 3-4mm. high. In the larger rudiments, the stipe 
and pileus were clearly differentiated, but no expansion took 
place and no spores were ever liberated. It was therefore clear 
that rapid and perfect production of fruit-bodies was associated 
in my cultures with the formation of clamp-connections, i.e. with 
the secondary or diploid condition of the mycelium, and that 
the production of imperfect fruit-bodies was associated with the 
non-formation of clamp-connections, i.e. with the primary or 
haploid condition of the mycelium. 
After the results embodied in Table I had been obtained, it 
was to be expected that mycelia of like signs, if paired, would 
not produce any clamp-connections. Each of six plates was 
therefore inoculated with two mycelia of (+) sign, and each 
of 18 plates with two mycelia of (—) sign. The results of this 
pairing, which are shown in Table IJ, did not conform with 
expectation, for only 16 of the 24 pairs remained without clamp- 
connections, while clamp-connections soon made their appear- 
ance in one of the six (++) pairs and in 7 of the 18 (——) pairs. 
It therefore became apparent that the phenomenon of hetero- 
thallism in Coprinus lagopus is much more complicated than I 
had at first imagined. 
Table II. Coprinus lagopus: The Effect of Pairing 
Monosporous Mycelia of Like Sign. 
Fruit-body 
Mycelial Sexual Clamp-connections development 
pairs signs after pairing in the plates 
15 x16 + + absent —_ 
16 x17 55 a5 7” — 
I7 x21 + + pe 
2I x22 -— + ry a 
27 x28 - - A — 
23 x26 == present _ 
28 x19 - - absent — 
25 x 46 = = os = 
48 x 47 =o hage ” aa 
18 x 47 a present — 
51 x15 + + absent — 
55 x16 4p ar present — 
2aIx Le = = Fe perfect 
23 x19 = - Fe - 
23 x25 - - absent imperfect 
23 27, == a 
23 x28 — = 
23 x29 a har ” ” 
26 x18 = = present perfect 
26 x19 = = s + 
26 x25 - - absent imperfect 
26 x27 - - present perfect 
26 x 28 — + 
absent imperfect 
26 x29 ” ” 
