THE THELEPHORACEAE OF NORTH AMERICA. IV^ 



EXOBASIDIUM 



EDWARD ANGUS BURT 



Mycologist and Librarian to the Missouri Botanioal Garden 



Associate Professor in the Henry Shaw School of Botany of 



Washington University 



EXOBASIDIUM 



Exohasidium Woronin, Naturforsch. Ges. Freiburg Ver- 

 handl. 4: 397-416. pi. 1-3. 1867. Saccardo, Syll. Fung. 6: 664. 

 1888. Hennings, in Engl. & Prantl, Nat. Pflanzenfam. (I.l**) : 

 103. 1897. 



The type species of the genus is Exohasidium Vaccinii Fuck, 

 ex Wor. 



Fungi parasitic in leaves, shoots, and flowers, which they 

 deform more or less, producing on the surface of these organs 

 an effused hymenium, rarely composed of basidia alone and 

 more usually felt-like and composed chiefly of interwoven 

 hyphae bearing basidia and conidiophores ; basidia simple; 

 spores white, simple or septate. 



Exohasidium resembles so closely in the thinness of its 

 fructifications such species of Corticium and Peniophora as 

 Corticium hyssinum, Peniophora asperipilata, P. pilosa, and 

 P. suhalutacea that I follow Saccardo and include it with the 

 above genera in the Thelephoraceae. Hennings in Engler & 

 PrantPs *Die Nattirlichen Pflanzenf amilien, ' has raised Ex- 

 ohasidium to ordinal rank but this is not justified by the 

 structure of the many fructifications of Exohasidium which I 

 have sectioned ; the illustrations in text-books of the structure 

 in section of the fructification are decidedly diagrammatic and 

 simplified. 



In his work already cited, Woronin gives a detailed account 

 of the morphology and life history of Exohasidium Vaccinii 

 and illustrates this account with three double plates. The 

 interest in this fungus which Woronin 's work aroused has 



^Issued October 8, 1915. 



Note. Explanation in regard to the citation of specimens studied is given 

 in Part I, Ann. Mo. Bot. Gard. 1 : 202, footnote. 



Ann. Mo. BOT. Gard., Vol. 2, 1915 (627) 



