266 Transactions British Mycological Soctety. 
the left indicate the numbers given to individual mycelia, while 
the (+) and (—) signs indicate that clamp-connections were 
present or absent respectively after the crossings had been 
effected. 
Table IV. Coprinus niveus: All Possible Pairings of 
Nine Monosporous Mycelia. 
I 2 4 5 6 7 8 9 
I ~ - + - ~ ~ - ~ 
2 = 5 = = = 9 hy) eee 
Bt) Sia, | Sn 
i ee ee 
5 ee 
6 = ~ ~ oe = = = = ss 
(Race its Pian hE le = 
8 = +: = = x 2 = = = 
9 ag tert ee <0 
As is shown in Table IV, Nos. 2 and 3 both failed to form 
clamp-connections with Nos. I, 2, 3, 5 and 6. Yet they are not 
identical sexually, for No. 2 formed clamp-connections with 
Nos. 7, 8 and 9, whereas No. 3 did not. Similarly Nos. 4 and 5 
did not form clamp-connections with Nos. 2, 7, 8 and g and yet 
are not identical sexually, for No. 4 formed clamp-connections 
with Nos. 1, 3, 5 and 6, whereas No. 5 did not. Moreover, when 
Nos. 4 and 5 were paired, they yielded clamp-connections. That 
the monosporous mycelia were pure was ascertained by making 
sub-cultures of these mycelia in plates at the same time that 
the pairings were effected. In none of these nine sub-cultures 
did any clamp-connections make their appearance. This is 
indicated in Table IV by the (—) sign for I x I, 2 X 2, 3 X 3... 
ay 
The results embodied in Table IV seem to show conclusively 
that the strain of Coprinus niveus with which my new work has 
been carried out is heterothallic but that the individual mycelia 
cannot be regarded as belonging strictly to two opposite strains, 
(+) and (—). Thus in my new work C. niveus has behaved 
sexually in the same manner as C. lagopus. 
VIII. Discussion. 
In both of my investigations upon the sex of Coprinus 
sterquilinus and C. stercorarius, mycelia of monosporous origin 
yielded clamp-connections regularly and readily gave rise to 
normal fruit-bodies. All the evidence so far obtained therefore 
strongly supports the view already expressed in my first paper, 
namely, that Coprinus sterquilinus and C. stercorarius are homo- 
thallic. 
