CHAPTER XV 



AUTOBASIDIOMYCETES 



In this class the sporophore or mycelial body may be of most 

 diverse form. The most essential character, however, is that ordi- 

 narily a portion of the sporophore is eventually differentiated into 

 a close layer, the hymenium, from which arise, in a palisade man- 

 ner, clavate or cylindrical basidia. Each basidium produces four 

 (occasionally two, six, or eight) unicellular basidiospores, each on 

 a relatively short sterigmatum. The fruit body, or sporophore, may 

 reach, in this class, the maximum size and complexity attained 

 among fungi. 



I. EXOBASIDIALES (EXOBASIDIACEyE) 



BREFELD, O. Die Gattung Exobasidium. Unters. a. d. Gesamtgeb. d. Myk., 



8: 12-18. 1889. 

 GEYLER, H. TH. Exobasidium Lauri, nov. sp. Bot. Zeit. 32 : 321-326. pi. 6. 



1874. 

 WORONIN, M. Ueber die Sclerotienkrankheit der Vaccinienbeeren. Me"m. 



acad. imp, de St.-Petersbourg 36 (Ser. 7): 28-30. 1888. 



The members of this order are distinguished from other Basid- 

 iomycetes chiefly in two characteristics, first, that the mycelium is 

 strictly parasitic, producing generally a gall-like hypertrophy made 

 up of mycelium and host tissue ; and second, that there is produced 

 no definite sporophore ; instead, the basidia break through the epi- 

 dermis of the host. 



Four sporidia are commonly produced (occasionally five or six). 

 The spores are curved, and germinate in nutrient media, so far as 

 known, after one or more cross partitions are formed. Germina- 

 tion is then more or less equivalent to a budding process, in which 

 numerous spindle-shaped cells are produced. 



The genus Exobasidium is most important, and the majority of 

 the species produce deformities upon different genera of heaths 

 (Ericaceae). 



439 



