HYSTERIALES 243 



Hy St er tales 



The Hysteriales include a group of some 670 species of asco- 

 mycetous fungi characterized by the possession of a distinctive 

 type of ascocarp called a hysterothecium. The fruiting body is 

 a small, black, elongate structure of hard or leathery texture, 

 which opens by a single narrow slit at maturity. The hystero- 

 thecium has been variously interpreted as an elongated perithe- 

 cium and as a compressed apothecium. Consequently the 

 Hysteriales have been classified by various systematists with both 

 the Pyrenomycetes and the Discomycetes. According to Bisby 

 (1913), this indicates clearly that they form a transitional group, 

 a fact which was first recognized by Rehm. Hohnel (1918), in 

 a rather radical classification of the group, would emphasize the 

 similarities between the Hysteriales and the family Lophiostoma- 

 taceae of the Sphaeriales. The similarity of the Hysteriales and 

 the Phacidiales has been pointed out by a number of workers. 



The Hysteriales include both parasitic forms and saprophytes 

 that produce the fruiting bodies on dead wood and bark. In the 

 customarily accepted classification [Lindau (1896)1, the group is 

 divided into 5 families, of which 2 will be considered here. In 

 the Hypodermataceae, which has been monographed by Darker 

 (1932), the hysterothecia are embedded within the substratum 

 and are overgrown by host tissue to form a clypeus above; in 

 the Hysteriaceae, the carbonaceous hysterothecia are freely ex- 

 posed. 



Elytroderma {Hypodemm) defomians, a typical representa- 

 tive of the Hypodermataceae, is parasitic on the needles and 

 stem tips of Finns ponderosa in the Pacific Northwest [Weir 

 (1916)]. Witches' brooms may be formed as the result of in- 

 volvement of the terminal shoots by this fungus. The needles 

 become browned at the tips and turn yello\\ ish where the black, 

 elongate hysterothecia are produced. A spermogonial stage also 

 is known, but the developmental history of the fungus has not 

 been followed. The asci, intermingled with paraphyses, contain 

 two-celled, fusiform ascospores. 



Closely related to Hypoderma is the Genus Lophodermium, 

 which differs only in the fiHform nature of its ascospores [Tehon 

 (1935)]. Lophodemninn pinastri is a serious parasite of pines, 



