378 CLASS BASIDIOMYCETEAE 



nor did sheets of mica, very thin sheets of silver, lead, and other sub- 

 stances. Apparently the repulsion is due to some sort of emanation from 

 the mycelium, perhaps gaseous. Experiments showed that certain nuclear 

 combinations give these mycelial repulsions but not others. Thus the 

 combinations ab X ab' and a'b X a'b' show "barrage" but not ab X a'b 

 or ab' X a'b'. Clearly the repulsion is between the b and b' mycelia. 

 The repulsion was also demonstrated between dicaryon mycelium and 

 monocaryon mycelium and between dicaryon mycelia where the two 

 sets of nuclei were different, e.g., (ab + a'b') X (a'b + ab'). This phe- 

 nomenon of barrage as well as the inhibition of growth does not occur in 

 all species. Brodie (1935) showed that barrage or "aversion" occurs also 

 in some strains of fungi growing naturally in wood. 



A peculiar phenomenon in connection with the occurrence of bipolar 

 and quadripolar sexual phases is that of "geographic races." This has 

 been studied in Coprinus by Hanna (1925) and by Vandendries (1924) 

 and extensively by Brunswik (1924) and in Ustilago by Bauch (1930, 

 1931). In some species of Coprinus the two sets of incompatibility factors 

 may be alike in fungi growing in the same locality but one or both sets 

 may be different in fungi (of the same species) growing in different local- 

 ities. In the latter case all sexual phases of one fungus would be compatible 

 with all sexual phases of the other fungus, while if only one pair is different 

 in the two fungi certain combinations will be incompatible. It is evident 

 that these are explained best on the hypothesis of multiple allelomorphs, 

 familiar to geneticists in both animals and plants. When either of the 

 factors produces an allelomorph by mutation a legitimate cross becomes 

 possible. Since these mutated factors are frequently discovered in fungi 

 from different geographic locations the term "geographic races" is often 

 used (see Kniep, 1928). In Ustilago longissima (Sow.) TuL, Bauch rec- 

 ognized over 15 allelomorphic strains of the A-a factors and about 8 of the 

 B-b factors. The resulting interfertility of all sexual phases of one collec- 

 tion of species with all sexual phases of another collection has been found 

 to be rather general. Thus Mounce and Macrae (1936) found complete 

 compatibility between collections made in different localities or on differ- 

 ent hosts in Gloeophyllum saepiarium (Wulf.) Karst. {Lenzites saepiaria 

 (Wulf.) Fr.) and in Trametes americana Overh., and Vandendries (1936) 

 showed its occurrence in Leptoporus adustus (Willd. ex Fr.) Quelet. 

 Barnett (1937) made similar observations for some of the Heterobasidiae. 



The Class Basidiomyceteae may be divided into three subclasses: 

 Teliosporeae (as a class in the earlier work of the author), Hetero- 

 basidiae, and Eubasidiae. They may be distinguished as follows: 



Teliosporeae : parasitic in the leaves, stems, f luits, and sometimes in the roots, 

 of Pteridophyta, Strobilophyta (Coniferae), and Anthophyta (Angio- 

 spermae). The septate parasitic mycelium is mostly intercellular in the host 



