Phylum Inophyta [ 145 



Most basidia discharge the spores actively, to a distance of a fraction of a milli- 

 meter. Buller (1929) observed that just before a spore is cast off a minute droplet 

 of liquid appears at the summit of the sterigma. This occurs in precisely the same 

 fashion in mushrooms, rusts, certain smuts, and the yeast-like organism Sporoholo- 

 myces. Buller inferred that the force which discharges the spore is surface tension 

 in the droplet. The fruits of Basidiomycetes are evidently adapted to the feebleness 

 of the mechanism by which the spores are discharged. If the fruits are cup-like, 

 they open laterally or downward. The basidia of mushrooms stand horizontally on 

 gills which are commonly less than one millimeter apart, allowing the spores to 

 fall from between them without touching them. 



The groups of Ascomycetes and Basidiomycetes are evidently related. Morels and 

 mushrooms, truffles and puffballs, taste alike. The technical scholar will be con- 

 vinced that the groups are related by the occurrence in both of a dikaryophase 

 stage, a character too strongly in contrast with those of the generality of organisms 

 to be a probable product of parallel evolution. Gaumann quotes an old opinion of 

 Vuillemin (1893), "qu'une baside est un asque dont chaque cellule-fille avant de 

 passer a I'etat de spore, fait saillie au dehors et se transforme en une sorte de conidie 

 pour mieux s'adapter au transport par la vent." In dealing with the Zygomycetes, 

 Gaumann emphasized the apparent evolution of conidia from endospores by evagina- 

 tion of the walls of the sporangia. Largely, as it seems, by Gaumann's influence, 

 Vuillemin's hypothesis has become generally accepted. 



Gaumann was disposed to derive the Basidiomycetes from something like Asco- 

 cortkiiim, and began his account of several of the groups of Basidiomycetes with 

 forms having scant flat fruits, or having basidia which spring directly from the 

 substratum or host. Linder (1940) suggested a derivation from Cupulata or Sclero- 

 carpa having operculate asci. He took note that many such asci open by producing a 

 vescicle, bounded by the stretched inner wall of the ascus, into which the asco- 

 spores pass. This led to the conclusion that the Basidiomycetes producing probasidia 

 are the lowest, and to this extent his reasoning appears cogent. He went on to identify 

 the rusts as the lowest Basidiomycetes, which seems far-fetched, the rusts being 

 distinctly a specialized group. 



The generally accepted groups of Basidiomycetes are those which were set forth 

 by Engler (1897, 1900), as follows: 



Subclass HEMiBAsron, having basidia bearing indefinite numbers of spores; the 

 smuts. 



Subclass EuBAsron, the basidia bearing definite numbers of spores. 



Order {Reihe) Protobasidigmycetes, the basidia divided into cells. 



Suborder {Unterreihe or Ordnung) ^uricularhneae, the basidia divided 

 by transverse walls. 



Sub-suborder [Unter ordnung) Uredinales, the rusts. 



tia Tritici, after Sartoris ( 1924) . k, 1, Basidia of Patouillardina cinerea after Martin 

 (1935). m, Basidium of Sebacina sublilacina after Martin (1934). n, Basidium 

 of Protodontia Uda after Martin ( 1932). o, p, younger and older basidia of Tulas- 

 nella phaerospora, after Martin (1939). q-t, Development of the basidium of 

 Guepinia Spathularia, after Bodman (1938). u-x, Russula emetica after Ritchie 

 (1941); binucleate primordium of basidium, fusion nucleus, homeotypic division, 

 development of basidiospores. y, z, Basidia of Lycogalopsis Solmsii after Martin 

 (1939). X 1,000 except as noted. 



