Omphalina ericetorum (Fries) M. Lange has already been described ([p. 232]): it grows on acidic soils and ascends into mountain areas where it frequently grows on algal scum which accumulates around Sphagnum plants.
Under these conditions the algal cells enter the base of the fungus and grow in the cavity of the stem and amongst those hyphae which constitute the base. This association, however, appears to be much closer in the two lichens Coriscium viride (Acharius) Vain and Botrydina vulgaris Meneghini which have long been classified as species of lichen of unknown affinity because no perfect state was known. Coriscium viride consists of blue-green overlapping plates or scales with narrow rounded often paler margins and which dry out greenish brownish grey. Botrydina vulgaris, in contrast, consists of dark green, gelatinous blobs drying out greenish brown.
Coriscium is now considered to be an association of an algae and a Basidiomycete, the latter being the agaric, Omphalina hudsoniana (Jennings) Bigelow, which resembles O. ericetorum but for the pinkish coloured stem. Botrydina may be a complex of several separate associations of an algae with different species of Omphalina. In the high mountains the association is with O. luteovitellina (Pilát & Nannfeldt) M. Lange a small uniformly bright yellow agaric, whilst in Sphagnum bogs it is with O. sphagnicola (Berkeley) Moser. Myxomphalia maura (Fries) Hora, a fungus typical of burnt ground, is also reported to take up this association in lowland woods and O. velutina (Quélet) Quélet appears to be capable of forming a loose relationship with algal cells also. This is a most interesting association and research work is still at an early stage. In the tropics and subtropical regions of the world, similar associations are found on rotten and decomposing trunks and stumps. In these examples the Basidiomycetes are frequently fairy-clubs, particularly species of Multiclavula (‘many small clubs’). A few species of this genus may be found also in North temperate woodlands. Botrydina also grows in Europe with Stereum fasciatum (Schw.) Fries and Athelia viride (Bres.) Parm. (see [p. 176]), and Odontia bicolor (Fries) Quélet is rarely collected without green algal cells buried in the thallus. Perhaps associations like this are much commoner than at first supposed. Probably the most remarkable of this group of poorly known organisms is Cora pavonia (Sw.) Fries which produces masses of interlocking fans; it is tropical and found in Brazil.
Mountain fungi: general remarks
There are several groups of mountain fungi, some mycorrhizal formers, some which prefer peaty soil and some which are associated with algae forming a loose relationship—the Basidiolichens. When the mountain top is covered with such dwarf willows as Salix herbacea or S. reticulata the leaves are cast each year, woody tissue develops above and below the ground; in fact all the processes taking place in our familiar woodlands are also taking place in these communities, the only difference being that the trees are dwarf. Indeed it looks quite odd to see normal sized agarics growing amongst the woody stalks of dwarf trees, the leaves of which are often one-tenth the size of the fruit-bodies, but this is what happens.
The mycorrhizal formers in these conditions include species of Russula (e.g. Russula alpina Möller & Schaeffer, R. xerampelina var. pascua Favre (see [p. 45])), Lactarius (e.g. Lactarius lacunarum Hora see [p. 50]), Cortinarius (e.g. C. anomalus (Fries) Fries see [p. 42]) and Amanita (e.g. Amanita nivalis Greville see [p. 56]). Subterranean fungi are also found, e.g. Elaphomyces see [p. 244], and, just as woodlands, valley bottoms have a saprophytic ground flora of toadstools so do the high mountain ‘woods’, and many familiar fungi of the lowerland areas are to be found there also, e.g. Mycena epipterygia (Fries) S. F. Gray, Mycena olivaceo-marginata (Massee) Massee (see [p. 88].)
The barer tops of the mountains, where large areas of moss are only to be found, support species of Hygrocybe, e.g. H. lilacina (Laestadius) Moser and H. subviolacea (Peck) P. D. Orton & Watling (see [p. 97]).
In the moist atmosphere on the hills in western Scotland, woodland-like floras containing familiar flowering plants are found on the mountain sides often much higher than in central Scotland. It is in such communities that typical woodland fungi are also to be found, e.g. Nolanea cetrata (Fries) Kummer (see [p. 101]).