The Brown Rollrim (Paxillus involutus) is one of the commonest mushrooms of birch woods, and one of the most deceptive. Its yellowish-brown cap becomes funnel-shaped with age and is sticky when wet, with a hairy edge that stays tightly rolled under. The crowded yellowish gills run down the short stem and bruise reddish-brown when touched, and the pale yellow flesh turns red-brown when cut.
It grows in mixed woodland, especially with birch and oak, and also with conifers, from June into November. It is widespread and common.
It was once eaten in parts of Europe, but it can trigger a sudden immune reaction that destroys red blood cells, sometimes after years of eating it without harm, and it has caused deaths. It must never be eaten. Funnels and milkcaps lack its rolled, downy edge and its gills, which peel easily from the cap.
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Distribution
Widespread and common
Habitat
In mixed woodlands especially with Betula and Quercus but also conifers.
Etymology
Paxillus is Latin for 'small peg' or 'stake'. involutus is Latin for 'rolled inwards', after the inrolled cap edge.
Associates
Betula, Picea, Quercus
Cap
The cap is yellowish-brown, 5-15 cm across, funnel-shaped and centrally depressed. The surface is smooth and viscid when wet, with a hairy, strongly inrolled margin, and the whole cap bruises reddish-brown.
| Colour | |
|---|---|
| Shape | Infundibuliform |
| Surface | Smooth, Viscid |
| Width | 5 - 15 cm |
| Margin | Hairy, Inrolled |
Gills
The gills are deeply decurrent and crowded, pale yellow darkening to brown with age. They bruise reddish-brown when handled and can be peeled easily from the cap.
| Colour | |
|---|---|
| Attachment | Decurrent |
| Spacing | crowded |
Flesh
The flesh is pale yellow and turns red-brown when cut, later browning. It has a pleasant smell and an acidic, sour taste.
| Colour | |
|---|---|
| Odour | Pleasant |
Stem
The stem is clavate, usually curved and yellowish-brown, often rather short and rarely larger than 1.5 cm in diameter. It bruises red-brown and darkens towards brown with age.
| Colour | |
|---|---|
| Shape | Clavate |
| Bruising |
Macrochemicals
Ammonia on the cap turns it brown.
Spores
| Colour | |
|---|---|
| Shape | Broadly ellipsoid |
| Ornamentation | Smooth |
| Size | 7-9.5 x 5-6 μm |
Classification
- ↳ Phylum: Basidiomycota
- ↳ Subphylum: Agaricomycotina
- ↳ Class: Agaricomycetes
- ↳ Subclass: Agaricomycetidae
- ↳ Order: Boletales
- ↳ Family: Paxillaceae
- ↳ Genus: Paxillus
Synonyms
- Agaricus adscendibus Bolton
- Agaricus contiguus Bull.
- Agaricus involutus Batsch
- Omphalia involuta (Batsch) Gray
- Paxillus involutus (Fr.) Fr.
- Paxillus involutus var. excentricus Fr.
- Paxillus involutus var. subinvolutus
Reference Sources
T. Læssøe, J. H. Peterson (2019) Fungi of Temperate Europe Vol. 1. Princeton University Press.
G. Kibby (2020) Mushrooms and Toadstools of Britain & Europe Vol. 1. Geoffrey Kibby.
Genus Paxillus
No other species found in this genus.
