KingdomFungiGenusCoprinusSpeciescomatus
Coprinus comatus
T0 · No known toxinsPublished 2026-09-25Spring / Autumn
The shaggy ink cap is one of the easiest large agarics in the temperate zone to identify and one of the easiest to lose: it autodigests from the cap margin inward at a rate you can watch. The identification is trivial while the scales are intact and impossible once they have dissolved, which is the entire discipline of collecting it.
Block 01 · Record
The closing window
A fresh fruit body is a white cylinder covered in overlapping shaggy scales with reddish-brown tips. Within about four hours at 20 degrees Celsius, the cap margin turns pink, then grey, then black, and the tissue liquefies from the margin inward until the whole cap has run down the stem as ink. Once the margin has blackened, the scales are gone and every diagnostic character has been destroyed. If you are photographing the species for a record, the photograph must be taken on the day the fruit body appears.
Spores and the black deposit
The spore print is black — in a thick deposit it is the colour of writing ink. Spores are 11-16 x 6-8 micrometres, ellipsoid, thick-walled, with a central germ pore that appears as a clear pore in the wall. They are inamyloid in Melzer's reagent and stain a deep blue in cotton blue, with the germ pore left as an unstained window. The gills are free, extremely crowded, and so thin that a young closed cap is translucent.
Habitat and season
This is a strongly nitrophilous soil saprotroph and it tracks disturbance rather than vegetation. Gravel drives, path edges, verges, lawns, spoil heaps and the margins of arable fields all produce it; it is often the first agaric to appear on soil that has been turned or spread within the previous two years. Fruit bodies are solitary to gregarious and often form dense troops in a strip 50 cm wide along a path. In temperate Europe it fruits mainly from September to November, with a second, smaller flush in April and May.
Discrimination: the smooth-capped coprinoids
Coprinopsis atramentaria grows in the same places at the same time and has a smooth, grey-brown cap with no shaggy scales and no ring. It contains coprine, which blocks acetaldehyde dehydrogenase; alcohol taken within about five days of a meal produces flushing, tachycardia, hypotension and vomiting, and the effect is the reason the species is listed at T2 rather than T0. The scaled cap of C. comatus is the whole separation, and it disappears within hours, so the decision has to be made on a fresh specimen.
Points to carry to the bench
- White cylindrical cap with overlapping shaggy scales tipped reddish-brown, and a movable ring.
- Gills free, very crowded, and deliquescing from the margin inward within about four hours.
- Black spore deposit; spores 11-16 micrometres, inamyloid, cyanophilic.
- A smooth grey-brown cap without scales is Coprinopsis atramentaria — T2 with alcohol.
| Cap | shape: Cylindrical to ellipsoid, 50-150 mm tall and 30-60 mm wide, remaining closed for most of its life and opening only shortly before it deliquesces.surface: White, covered in recurved shaggy scales that are cream at the base and reddish-brown at the tips; the scales are arranged in overlapping rows.margin: Appressed to the stem when young, then separating and turning pinkish to black as deliquescence begins. |
|---|---|
| Gills | attachment: Free, with a clear 1-2 mm gap between the gill backs and the hollow stem apex.spacing: Very crowded, 5-7 gills per millimetre, the gills so thin that light passes through a young closed cap.edge: White then pink then black; the sequence runs from the cap margin inward and takes about four hours at room temperature. |
| Spore print | Ellipsoid, thick-walled, with a central germ pore that shows as a clear pore in the wall.Smooth, with a truncate base; the spore wall is about 1 micrometre thick and stains strongly in cotton blue. |
| Habitat and season | Saprotrophic on disturbed, nutrient-enriched soil: verges, gravel drives, path edges, lawns, construction spoil and the margins of arable fields. Strongly nitrophilous and often the first agaric to appear on newly turned ground. |
Block 02 · Chemistry
| Reagent | Verdict | Reaction | Weight |
|---|---|---|---|
 MELZ | inamyloid | Spore wall stays dark yellow-brown; no blue-black amyloid development. | 3.00 |
 KOH5 | negative | Cap surface unchanged; the reddish-brown tips of the scales are stable to alkali. | 2.00 |
 FESO4 | negative | Flesh shows no reaction within 60 s. | 3.00 |
 COTTON | cyanophilic | Spore wall stains deep blue, the central germ pore remaining as an unstained window. | 2.00 |
Injury stain None. The cap and stem stay white until autodigestion begins, and the blackening that follows is a developmental process, not an injury reaction. Any specimen that reddens or blues at a bruise belongs somewhere else.
Block 03 · Confusion
| Separating character | This record | Confused with |
|---|---|---|
| A smooth, grey-brown cap with no shaggy scales and no ring; the two species share a habitat and a season, and the scaled cap is the whole separation. | Coprinus comatusT0 | Coprinopsis atramentaria▲ +2 |
| Much smaller, ochre-brown, growing in dense clusters on buried wood, with a cap dusted in glistening mica-like granules rather than shaggy scales. | Coprinus comatusT0 | Coprinellus micaceus▲ +0 |
| A parasol-shaped agaric passing near the same verges, with a green spore print and gills that never deliquesce; also a ring that does not slide. | Coprinus comatusT0 | Chlorophyllum molybdites▲ +1 |
Toxicity ladder
No toxin has been isolated or reproduced in feeding trials, and decades of documented ingestion carry no reproducible syndrome. T0 is a statement about the chemistry of the species, never a statement about a specimen in your hand.
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