Macrolepiota mastoidea (Fr.) Singer - Slender Parasol

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Agaricaceae

Macrolepiota mastoidea - Slender Parasol

Macrolepiota mastoidea, the Slender Parasol, favours calcareous woodlands and grasslands. These large mushrooms also occur in coastal dunes in what would otherwise be acidic areas where it not for the presence of broken sea shells that raise the alkalinity of the thin soil. In some dune systems Slender Parasols appear in crowds.

Distribution

Slender Parasols are fairly common in Britain and Ireland; they also occur across most of Europe.

Slender Parasols in a sand-dune habitat, North Wales

Taxonomic history

The basionym (base name) of this mushroom dates from 1821, when Elias Magnus Fries included it in his Systema Mycologia, calling it Agaricus mastoideus.

Earlier, in 1801, Danish botanist Heinrich Christian Friedrich Schumacher (1757 - 1830) had illustrated this mushroom, calling it Agaricus umbonatus. (In the early days of fungal taxonomy, almost anything with gills was placed in a gigantic Agaricus genus, now slimmed down to more manageable proportions as many of its former residents have been moved into more appropriate accommodation in new genera.)

Macrolepiota mastoidea - Slender Parasol , France

Synonyms of Macrolepiota mastoidea include Agaricus mastoideus Fr., Agaricus gracilentus Krombh., Lepiota mastoidea (Fr.) P. Kumm., Lepiota gracilenta (Krombh.) Quél., Lepiota umbonata (Schumach.) J. Schröt., Lepiota rickenii Velen., Macrolepiota gracilenta (Krombh.) Wasser, and Macrolepiota rickenii (Velen.) Bellù & Lanzoni.

Etymology

The specific epithet mastoidea is probably not a reference not to the bony prominence (mastoid) located behind the human ear but rather based on the prefix masto- meaning something to do with a woman's breasts and their nipples. These short-lived mushrooms (see picture above) are surely no long-term substitute for the real thing.

Identification guide

Cap of Macrolepiota mastoidea

Cap

Initially spherical and pale brown with a darker brown area near the crown that breaks into scales, the cap expands until it is flat with a small umbo. The flesh of this mushroom gradually turns brown but does not redden noticeably when cut or bruised.

The cap diameter at maturity ranges between 5 and 15cm.

Gills and stem of Macrolepiota mastoidea

Gills

The broad, crowded gills, some of which fork, are white or pale cream and free, terminating a small distance from the stipe.

Stem

A double ring, the upper face pale and the lower face brown, usually persists around the stem but often becomes movable and occasionally falls to the base. The stem surface is white and is covered with small, closely spaced yellowish-brown scales.

Slightly bulbous at the base, the stem tapers inwards towards the apex; its diameter ranges from 0.6 to 1.5cm, and the height varies between 6 and 16cm.

Spores of <em>Macrolepiota-mastoidea</em>

Spores

Ellipsoidal, smooth, 13-16 x 8-9.5µm; with a germ pore; dextrinoid.

Show larger image

Spore print

White or pale cream.

Odour/taste

Odour slight, 'mushroomy'; taste mild but not distinctive.

Habitat & Ecological role

Saprobic, in woodland clearings and in grassy areas next to woodland; also on calcareous sand dunes.

Season

July to November in Britain and Ireland; later in the year in southern Europe.

Similar species

Macrolepiota procera, the Parasol, is larger and has a snakeskin-like pattern on its stem.

Chlorophyllum rhacodes, the Shaggy Parasol, has reflexed scales and a smooth stipe; its flesh reddens when cut or bruised.

Culinary Notes

The Slender Parasol is a good edible species, but if you do gather these mushrooms to eat then please be aware that the somewhat similar Shaggy Parasol Chlorophyllum rhacodes is a toxic toadstool and can cause very serious stomach upsets. For advice on preparation and cooking these kinds of fungi see the culinary notes under Parasol, Macrolepiota procera.

Reference Sources

Fascinated by Fungi, Pat O'Reilly, 2011

BMS List of English Names for Fungi

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

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