SPOROBOLOMYCES 205 



One of the most remarkable discoveries in connexion with the 

 Hymenomycetes is that, in certain species of Agaricineae, there are 

 haploid fruit -bodies as well as diploid. Bauch 1 has investigated 

 two races of Hygrophorus (Camarophyllus) virgineus, one with 2- 

 spored basidia and the other with 4-spored basidia, and he has 

 shown that the fruit-body of the 2-spored race is haploid through- 

 out, while that of the 4-spored race is diploid throughout. In the 

 2-spored race, the walls of the cells of the fruit-body are without 

 clamp-connexions, there is only one nucleus in each cell, each young 

 basidium contains but a single nucleus so that a union of two nuclei 

 in the basidium does not take place, the basidial nucleus divides 

 once only, and a single nucleus passes up into each of the two spores. 

 On the other hand, in the 4-spored race, the walls of the cells of the 

 fruit-body bear clamp-connexions, there are two conjugate nuclei 

 in each cell, each young basidium contains two nuclei which fuse 

 together, the fusion nucleus divides twice and thus produces four 

 nuclei, and these four nuclei pass upwards through the sterigmata 

 into the four spores. Hanna 2 has succeeded in growing Coprinus 

 lagopus, which is a heterothallic species, in the haploid condition 

 for ten successive generations. His ten mycelia and ten fruit - 

 bodies with all their spores were all unisexual and of the same sex 

 as the original spore sown at the beginning of the experiment. The 

 investigations on haploid fruit-bodies show that uninucleate haploid 

 cells can develop into perfect basidia, thus proving that the develop- 

 ment of a basidium is not dependent on the presence of two nuclei 

 of opposite sex or on the occurrence of karyogamy. A Sporobolo- 

 myces yeast cell, before spore-production, contains but a single 

 nucleus, so that karyogamy cannot take place in its interior. In 

 this respect it exactly resembles a haploid basidium of the 2-spored 

 race of Hygrophorus virgineus investigated by Bauch. The non- 

 occurrence of conjugate nuclei and of karyogamy in Sporobolomyces 

 cannot therefore be accepted as proving that this genus does not 

 belong to the Basidiomycetes. 



1 R. Bauch, " Untersuchungen iiber zweisporige Hymenomyceten. I. Haploide 

 Parthenogenesis bei Camarophyllus virgineus" Zeitschrift fiir Botanik, Bd. XVIII, 

 1926, pp. 337-387. 



2 W. F. Hanna, " Sexual Stability in Monosporous Mycelia of Coprinus lagopus,'''' 

 Annals of Botany, Vol. XLII, 1928, pp. 379-389. 



