Hysterothecia are capable of opening partially to reveal a lenticular (lens-shaped), disk-like hymenium or closing tightly in response to relative humidity.
Bitunicate (double-walled) asci are borne in a basal layer and at maturity are typically club-shaped to cylindrical, bearing eight ascospores, overlapping in two series, ranging from hyaline to dark brown, obovoid, clavate, ellipsoid or fusoid.
Ascospores are highly diverse in septation, and range from didymospores to phragmospores to dityospores, at times surrounded by a gel coating, and often show bipolar asymmetry.
[3][4] The Hysteriaceae are panglobal in distribution[3][5][6][7][8][9][10][11][12][13][14][15] and are primarily lignicolous or corticolous (living on bark), although recently a saxicolous and apparently lichenized species has been described from Tasmania.
Due to the seemingly transitional nature of the hysterothecium, neither fully open nor closed, hysteriaceous fungi have been placed in the discomycetes and pyrenomycetes about equally by various mycologists throughout the 19th Century.
[27] In his Systema Mycologicum, Fries (1823)[28] initially considered hysteriaceous fungi to belong to the pyrenomycetes and placed them in the order Phacidiacei, but later (1835) placed them in his new class discomycetes, stating: “Transitum sistunt ad Discomycetes, sed discum verum non monstrant.”[29] François Fulgis Chevallier (1826) recognized the unique nature of the hysterothecium and was the first to segregate hysteriaceous fungi into a new order, the Hysterineae, which he considered as pyrenomycetes distinct from Fries’ Phacidiei.
[31] Giuseppe De Notaris (1847) considered the Hysteriaceae to belong to the pyrenomycetes and used spore pigmentation to classify hysteriaceous fungi into the Phaeosporii and the Hyalosporii.
[35] Job Bicknell Ellis and Benjamin Matlack Everhart (1892), in their North American Pyrenomycetes, tentatively included the Hysteriaceae, but stated that they had not at first intended to do so due to the transitional nature of the hysterothecium.
[37] Duby (1862) considered hysteriaceous fungi to belong to the pyrenomycetes and proposed two sections, the Hystériées to include Hysterium, Glonium, and Actidium Fr.
[38] Although Duby’s (1862) method of classification, based on dehiscent versus nondehiscent asci, was not followed by subsequent workers, he was the first to propose dividing hysteriaceous fungi into what was later to become two distinct families.
Unlike the hymenoascomycetes, the loculoascomycete ascoma originates prior to karyogamy in the dikaryon, with the correlated character state being the functionally two-walled ascus which ruptures in a fissitunicate (like a Jack-in-the-box) fashion.
[48] Initially, Luttrell (1953) was unsure whether the Hysteriaceae justified ordinal status, stating that the elongated hysteriaceous locule alone may not appear to be sufficient for the recognition of a separate order and the dothideaceous nature of the centrum at the earliest stages was not observed in his study.
[46] Hans Zogg (1962) acknowledged the heterogeneity of the classical Hysteriales[3] and, following Duby (1862),[38] divided hysteriaceous fungi into two families, namely the Hysteriaceae s. str.
Although Luttrell held a very wide concept of the Hysteriales (1973), he did not recognize the family Lophiaceae, instead proposing a subfamily within the Hysteriaceae to accommodate mytilinidiaceous forms.
Later, Barr (1983) abandoned the Hysteriales and placed the Hysteriaceae within the Pleosporales due to the presence of cellular pseudoparaphyses, asci borne in a basal rather than peripheral layer and ascospores typically showing bipolar asymmetry.
[4] The genus Hysteropatella Rehm is transitional with paraphysoids and a well-developed pseudoepithecium, but the peridium, thickened base of the ascoma and cylindric asci are all features of the Hysteriaceae.