HEMIASCOMYCETES 



267 



as in the Saccharomyceteae. In Arachniotus candidus, in 

 addition to a sexual mode of reproduction, oidia are pro- 

 duced by the breaking up into minute reproductive 

 bodies of branched hyphae. 



The Gymnoasceae are considered to show affinity with 

 Onygena, as indicated by Ward's researches on the last- 

 named genus. 



Most abundant in Europe, but probably widely dis- 

 tributed. 



Dale, Ann. Bot.^ 17, p. 571 (1903). 



Eidam, Cohris Beitr., 3, p. 385 (1883). 



Ward, Phil. Trans. Roy. Soc., ser. B., 191, p. 269 (1899). 



Exoasceae 



Parasitic on living plants. Mycelium mostly subcuti- 

 cular, rarely penetrating deeper into the tissues, intra- 

 cellular. A plexus of hyphae is developed just below the 

 cuticle, which becomes differentiated into ascogenous and 

 vegetative hyphae. The ascogenous hyphae develop 

 directly into asci which rupture the cuticle and form a 

 palisade-like arrangement of asci standing side by side on 

 the surface of the matrix, entirely devoid of any perithecium 

 or covering of any kind. In some instances the ascogenous 

 cell grows out at once into the ascus, in other cases the 

 ascus is separated from the cavity of the ascogenous cell by 

 a transverse septum. 



In Exoascus the mycelium is perennial in the tissue of 

 the host. In Taphrina the mycelium is localised in 

 deciduous organs, and is annual in duration. The spores 

 are hyaline and one-celled, 4-6 in an ascus. In Taphrina 

 the spores reproduce by budding after the manner of 



