(Revised July 1999)
| The following trial key has been compiled by members of the North West Fungus Group in the UK |
| 1 | Small cap up to 15mm., usually on decaying fungi. | 2 |
| Large cap usually greater than 20mm. | 5 | |
| 2 (1) | Stipe with lateral outgrowths throughout length. (rare but unmistakable) | C. racemosa ( Pers.) Quél |
| Stipe plain. | 3 | |
| 3 (2) | Fungus with sclerotium. | 4 |
| Fungus without sclerotium. | C. cirrhata ( Schum.) Kummer | |
| 4(3) | Sclerotium dark brown to black. | C. tuberosa ( Bull.) Kummer |
| Sclerotium ochraceous. | C. cookei ( Bres.) J.D.Arnold | |
| 5 (1) | Stipe spindle-like or longitudinally fibrous./Smell unpleasant, of drains, rotten cabbage or garlic. | 6 |
| Stipe pliable or only slightly fibrose at base./Smell indistinct or not unpleasant. | 8 | |
| 6 (5) | Cap not translucently striate, or only at margin. Stipe pale. (rare) | C. impudica ( Fr.) Singer |
| Cap translucently striate, at least to half radius. Stipe dark, especially in lower half. | 7 | |
| 7 (6) | Two species, both of calcareous beech woods, best separated by microscopic characters, included here lest the previous species be misidentified. | |
| Usually on leaf litter. | Micromphale brassicolens (Romagn.) Orton | |
| Usually on wood. | Micromphale foetidum (Sow.:Fr.) | |
| 8 (5) | Stipe hairy or downy, at least at base. | 9 |
| Stipe smooth or striate, not hairy or downy. | 17 | |
| 9 (8) | Gills distant to normally spaced. | 10 |
| Gills remarkably crowded. Stipe velvety throughout, beige or buff, concolorous with cap or darker below (but brown when wet). Usually growing in large clumps. | C. confluens ( Pers.) Kummer | |
| 10 (9) | Stipe shaggy hairy in lower part. | 11 |
| Stipe downy velvety or pruinose overall. | 16 | |
| 11 (10) | Whole fruitbody very dark purple-brown. | 12 |
| Fruitbody paler. | 13 | |
| 12(11) | Amongst grass in parks and gardens. (not rare in S. England) | C. obscura Favre ss. Phillips |
| Beech litter on calcareous soil. (uncommon) | C. fuscopurpurea ( Pers.) Kummer | |
| (Note that we use this name in the sense of A&N and FAN, see also C. fagiphila below) (Misapplied synonym C. alkalivirens.) C. obscura and C. fuscopurpurea may well prove to be separate species. The former differs in lacking the green colour change of hyphal elements with KOH. | ||
| 13 (11) | Gills remarkably distant. Taste sharp. Cap hazel tan wrinkled with age. Stipe concolorous. Usually with deciduous trees. | C. peronata ( Bolt.) Singer |
| Gills somewhat distant to normally spaced. Taste mild, to slightly bitter. (3 rare species) | 14 | |
| 14 (13) | Attached to pine needles. Cap date brown, drying paler, gills concolorous. (rare) | C. putilla (Fr.:Fr.) Sing. |
| Broadleaf woodland. | 15 | |
| 15 (14) | Beech litter on calcareous soil, occasionally oak. (rare) | C. fagiphila Velen. |
| (This species is C. fuscopurpurea in the sense of the New Check List 1960, Fungi of Switzerland and Courtecuisse & Duhem, C. konradiana for Flora Agaricina Neerlandica) | ||
| On leaves of deciduous trees. Betula, Salix, Fagus,Quercus. (very rare) | C. tergina ( Fr.) Limdell | |
| 16 (10) | Cap red brown, hygrophanous. | C. inodora (Pat.) Orton |
| Appearance of Marasmius oreades. Alder carrs. (rare species) | C. oreadoides (Pass.) Orton | |
| 17 (8) | Stipe logitudinally fibrillous-striate, often twisted. | 18 |
| Stipe smooth, polished. | 23 | |
| 18 (17) | Stipe spindle shaped, rooting, concolorous or darker at base, cap becoming brown spotted. Deciduous woodland, usually with oak. | C. fusipes ( Bull.) Quél |
| Stipe not spindle shaped. | 19 | |
| 19 (18) | Cap pale, white, usually with rusty brown spots. (Can become brown in exposed montane situations) | C. maculata ( A&S.) Quél |
| Cap darker, to dark red-brown, without brown spots. | 20 | |
| 20 (19) | Cap hygrophanous, feel of butter. Stipe tapers to broad base. Woodland. | 21 |
| Cap not hygrophanous, or scarcely so. Coniferous woodland. | 22 | |
| 21 (20) | Cap and stipe paler horn brown. (common species) | C. butyracea v. asema (Fr.) |
| Cap and stipe reddish brown, drying paler. (much less common and favouring more acid soils) | C. butyracea ( Bull.) Quél | |
| 22 (20) | Cap orange brown to red brown. Stipe white to concolorous. New Forest, Wales and northern. | C. distorta (Fr.) Quél |
| Cap very dark red brown - chestnut. Stipe more or less concolorous. (rare) Scottish Highlands only. | C. prolixa ( Hornem.) Gill | |
| (These species are very similar and can only be reliably separated microscopically. C. distorta is regarded as a variety of C. prolixa by A&N) | ||
| 23 (17) | Stem red or red brown. | 24 |
| Stem differently coloured, paler. | 25 | |
| 24 (23) | Growing with conifers, in dense clumps, in the Scottish Highlands. | C. acervata (Fr.) Kerst |
| Growing with deciduous trees. | C. erythropus ( Pers.) Kummer | |
| 25 (23) | Cap (and stipe) yellow to ochre brown, striate when moist. | 26 |
| Cap darker, red brown to chestnut. | 27 | |
| 26 (25) | Stipe base usually not bulbous. Fruitbody with ochraceous colours. Rhizomorphs white to ochraceous. Summer to Autumn. | C. dryophila (Bull.) Kummer |
| Stipe base usually distinctly and abruptly bulbous, to 2 cm. Fruitbody straw colour. Rhizomorphs pink. Found early in the year. (uncommon) | C. aquosa (Bull.:Fr.) Kummer | |
| 27 (25) | Woodland. Cap reddish brown to chestnut. (gills usually yellow, but can be white, neither form common.) | C. ocior ( Fr.) Quél |
| (Synonyms: extuberans, succinea, exsculpta, luteifolia) These species cannot be separated by microscopic characters, according to Noordeloos. Descriptions of stipe colour vary widely. | ||
| Montane, Hebrides and Scottish Mountains. Cap deep red-brown, centre darker. Gills whit to cream. Only separated by microscopic characters. | C.alpina Vilgalys & Miller |