Mycena flavoalba(pink form)

=Mycena floridula sensu Kühner

Mycena floridula

© A. Aronsen
SWEDEN, Gotland, Fårö 26 Sept. 2011

Widely distributed in southern parts of Norway, and apparently also in the rest of Northern Europe. Autumn. Not very common, among grass and mosses. Records in The Norwegian Mycological Database.

Pileus 5-15 mm across, at first hemispherical, then conical to convex, occasionally somewhat depressed centrally, glabrous, hardly or very shallowly sulcate, translucently striate or not, hygrophanous, when very young bright coral red with the margin somewhat paler, then pink with a whitish margin, fading to straw yellow with a faint pinkish tinge and paler margin. Lamellae 18-27 reaching the stipe, ascending, narrowly to somewhat broader adnate, sometimes decurrent with a very short tooth, becoming intervenose, yellowish white to pale pink with paler edge. Stipe 30-65 x 1-1.5 mm, hollow, terete, straight, equal, glabrous except for the pruinose apex, white to yellow-white, rarely with a slight tint of the pileus but very much paler; the base densely covered with white fibrils. Odour and taste indistinctive.

Basidia 24-30 x 5.5-6 μm, clavate, 4-spored. Spores 7-9.5 x 3.5-5 μm, Q 1.5-2.1, Qav 1.9, pip-shaped to almost cylindrical, smooth, non-amyloid. Cheilocystidia 40-53 x 7-11 μm, occuring mixed with basidia, fusiform to lageniform, smooth and simple, more rarely apically furcate. Pleurocystidia similar. Lamellar trama not vinescent in Melzer's reagent. Hyphae of the pileipellis 1.5-4 μm wide, densely covered with variously shaped excrescences, some up to 10 x 5 μm. Hyphae of the cortical layer of the stipe 1.5-3.5 μm wide, smooth, caulocystidia 7-22 x 5-8 μm, clavate, globose or subglobose. Clamp connections present at all tissues.

This taxon has usually been named as 'Mycena floridula'. It is rather easily identified on account of the pink colour of the cap, but it has been suggested that it is merely a colour form of M. flavoalba since there seems to be no microscopical characters distinguishing the two taxa. Besides, 'M. floridula' has been reported to fade in colours so much that it is no longer possible to distinguish the species from M. flavoalba. An important piece of information, however, was provided by A. Hausknecht (Maas Geesteranus 1991: 400), who had observed that the faded specimens of 'M. floridula', when placed in his drying apparatus, regained their original colour and have stayed red ever since, whereas no colour change was observed in the drying specimens of M. flavoalba. This character has been confirmed by my own observations.

Sometimes it can be difficult to separate 'M. floridula' from M. adonis, although the latter generally is brighter in colour. Following Kühner's description Maas Geesteranus (1990: 165) used the colour of the lamellae and the pileus to distinguish between the two taxa. His statement was that in M. adonis the lamellae are 'delicately pink, turning whitish to white' whereas they are 'bright pinkish red to coral red at their bases, pallescent' in M. floridula. He also claimed that in M. adonis the pileus has 'no trace of yellow, nor turning yellowish when fading. In M. floridula the pileus is 'turning bright yellow with age'. To my experience the colour of the lamellae is not a good character, while it is probably correct that the pileus will not turn into a yellowish colour in M. adonis, although it may faint to almost white.

The shape of the spores is a good character to distinguish 'M. floridula' from M. adonis. In 'M. floridula' (which is 4-spored) the spores are pip-shaped to cylindrical with an average Q value >1.8. The spores in M. adonis are broader, with an average Q value < 1.8. I have, however, only measured spores from 2-spored M. adonis. It may be that 4-spored basidia is producing somewhat narrower spores. According to Maas Geesteranus (1990) the spores of 4-spored M. adonis are of the same size as those of 'M. floridula'.

A good example of how confusing this section is, is the key by Robich (2003: 27). In addition to the lack of yellow colours in the pileus of M. adonis, the difference between M. adonis and M. floridula, according to this key, is that the lamellar edge is white in the former and pale pink in the latter. This is not corresponding to my own experience, and it seems not to be true from what can be seen from his colour photo of M. floridula (p. 40). Robich has probably only seen 2-spored M. adonis, and hence the spore shape is different from M. floridula. In his description of the basidia he only mentioned the 2-spored form, but later he said that the 4-spored form possesses clamps.

Another confusing point was reported by R. Lebeuf (2011), who reported M. floridula with 2-spored basidia and slightly larger spores from Canada.

A problem with 'Mycena floridula' has been that, although the taxon has been quite precisely described, the name has been illegitimate. Maas Geesteranus (1990) considered Fries's original description of Agaricus floridulus as a likely synonym of M. adonis but he did not give the taxon(M. floridula) a new formal name. This view is also followed by Index Fungorum.

Aronsen & Larsson (2016) examined and analysed nine ITS sequences of 'Mycena floridula', five sequences of M. flavoalba and five of M. adonis. Their results showed that the 'M. foridula' collections are conspecific with a part of the M. flavoalba material, while the other part of the M. flavoalba material constitutes a sibling species currently not circumscribed. At the present web site 'M. floridula' therefore is treated as a pink form of M. flavoalba.

See also the key to sect. Adonideae.


Images on the Internet:


© Arne Aronsen 2002-2018