The larger cup fungi in Britain: part 4: Sarcoscyphaceae and Sarcosomataceae

Abstract

The first article in this series (Spooner, 2000) provided an introduction to cup fungi and noted that most of the larger species belong to the order Pezizales. These are commonly known as the ‘operculate cup-fungi’ based on their ascus structure – mostly thinwalled and dehiscing by an apical ‘lid’ or operculum and include an estimated 300 or so species in Britain. A key to the 13 families of Pezizales represented in Britain was provided, and two subsequent articles (Spooner 2001a, 2001b) provided keys for the identification of the British species of the family Pezizaceae. In the present article two further families, Sarcoscyphaceae and Sarcosomataceae, are considered. These families are closely related to each other, and indeed some authors have preferred not to separate them but to merge all their included species in a single family Sarcoscyphaceae. They differ significantly from other Pezizales most notably in ascus and spore characters. The asci, always non-amyloid, are rather thick-walled, with the operculum usually subapical, positioned slightly to one side of the apex – often termed ‘suboperculate’. In addition, the spores of these fungi are commonly asymmetrical, often curved or inequilateral, unlike those of almost all other Pezizales.They are also unusual in being multinucleate, otherwise characteristic in the Pezizales only of Morchellaceae. Under the microscope the ascus and spore characters are usually fairly easy to observe, but many of the species that belong in this group can be so recognised either by their particularly brightly coloured apothecia (Sarcoscyphaceae) or their dull, brown to blackish colours (Sarcosomataceae). The bright, usually red or orange colours are due to the presence of abundant carotenoid pigments, these usually being absent in the dark-coloured species in which melanin-like pigments occur instead.The apothecia of these fungi vary greatly in size and shape, some being small, sessile, discoid structures others being large, cupulate, often stalked and sometimes even compound.They occur mostly in spring and are saprotrophs, occurring on the ground or on rotting wood. Although Sarcoscyphaceae exhibits its greatest diversity in the tropics, both of these families are virtually cosmopolitan in distribution. However, they include between them no more than about 60 species in all and, in Britain, just nine species ranged in six genera have been recorded. Furthermore, it should be noted that some of the British species are rare and, regrettably, two of them, the beautiful and distinctive Microstoma protracta, and the obscure Pithya vulgaris, both known here from ancient records from only single localities, are surely now extinct in Britain. A key plus brief descriptions for the British genera and species are provided in this account.