Public Description of Rhodotus palmatus (Bull.) Maire

Title: Public Description (Default)
Name: Rhodotus palmatus (Bull.) Maire
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Description status: Approved
 (Latest review: 2010-04-14 17:58:59 PDT (-0700) by nathan)

Taxonomic Classification:

Domain: Eukarya
Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Order: Agaricales
Family: Physalacriaceae

General Description:

The cap is convex but flattens with age; it is typically 2 to 6 centimetres (0.8 to 2.4 in) wide. Cap margins are lightly to strongly rolled inwards.

Specimens have been found with the surface colors ranging from salmon-orange to pink to red. The cap surface typically has a conspicuous network of lightly colored ridges or veins that outline deep narrow grooves or pits – a condition technically termed sulcate or reticulate. The texture of the cap surface is gelatinous, although the internal flesh is firm, and pinkish in color. The gills have an adnate attachment to the stem, i.e., broadly attached to the stalk slightly above the bottom of the gill, with most of the gill fused to the stem; the gills are thick, packed close to each other, with veins and color similar to, but paler than the cap. The stem is 1.5 to 3.0 cm (0.6 to 1.2 in) tall by 0.4 to 0.6 cm (0.2 to 0.2 in) thick (usually slightly larger near the base), and may be attached to the bottom of the cap in a central or lateral manner. It is sometimes seen “bleeding” a red- or orange-colored liquid. The spore print has been described most commonly as pink, but also as cream colored. The species has no distinguishable odor, and a bitter taste.

Microscopic features

The spores of R. palmatus are roughly spherical, with dimensions of 6–7.2 by 5.6–6.5 µm; the spore surface is marked with numerous wart-like projections (defined as verricose, in mycological jargon), typically 0.5–0.7 µm long The spores are non-amyloid, i.e., unable to take up iodine stain in the chemical test with Melzer’s reagent. The spore-bearing cells, the basidia, are club-shaped and 4-spored, with dimensions of 33.6–43.2 by 5.6–8 µm. Although this species lacks sterile cells called pleurocystidia (large sterile cells found on the gill face in some mushrooms), it contains abundant cheilocystidia (large sterile cells found on the gill edge) that are 27.2–48 by 4.8–8 µm in size. Clamp connections are present.

The content for this page is adapted from the Wikipedia article which was contributed to by Sasata. See that article for detailed references, authorship and references.


An uncommon species, it has a circumboreal distribution, and has been collected in eastern North America, North Africa, Europe, and Asia.

R. palmatus has been reported from Canada, Iran, Hungary, Italy, Slovakia, West Germany, Korea, the area formerly known as the USSR and Japan. The species gained legal protection in Hungary in 2005. The 1993 National Environmental Status Report for the Baltic countries Estonia, Lativa and Lithuania report is as “Extinct or probably extinct”. In the United States it has been found in Indiana, and elsewhere in eastern North America. Although often described as “rare”, a 1997 study suggests that it may be relatively common in Illinois. It has been suggested that the increase in the number of dead elms (resulting from Dutch elm disease) has contributed to its resurgence.


This species grows scattered or in small groups on rotting hardwoods, such as elm (genus Ulmus), basswood (Tilia), and maple (Acer); it prefers low-lying logs in areas that are periodically flooded and that receive little sunlight, such as forest areas shaded by canopy. Rhodotus palmatus tends to fruit in cooler and moister weather, from spring to fall in the United States, or fall to winter in Europe and Britain.

Look Alikes:

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Depending on the source consulted, the edibility of Rhodotus palmatus is typically listed as unknown or inedible.


The species was originally described as Agaricus palmatus in 1785 by French botanist Jean Baptiste François Pierre Bulliard. The species name is derived from the Latin palmatus, “shaped like a hand”, possibly a reference to the resemblance of the cap surface to the lines in the palm of a hand.34 It was transferred to the then newly described genus Rhodotus in a 1926 publication by René Maire.

The placement of the genus Rhodotus in the Agaricales is uncertain, and various authors have offered solutions to the taxonomic conundrum. In 1951, Rolf Singer placed Rhodotus in the Amanitaceae because of similarities between the tribes Amaniteae and Rhodoteae, such as spore color and ornamentation, structure of the hyphae and trama, and chlamydospore production during culture growth. In 1953, Kühner and Romagnesi placed Rhodotus in the Tricholomataceae family – a traditional “wastebasket taxon” – on the basis of spore color. In 1969, Besson argued for the placement of Rhodotus with the Entolomataceae after studying the ultrastructure of the spores. In 1988, a proposal was made to split the Tricholomataceae family into several new families, including the Rhodotaceae to contain the genus Rhodotus. A 2000 study of the nuclear large subunit ribosomal DNA from a wide variety of Agaric fungi corroborated Kühner and Romagnesi’s placement of Rhodotus in the Tricholomataceae; in the study it was shown to be part of a clade containing species such as Cyptotrama asprata, Marasmius trullisatus, Flammulina velutipes, Xerula furfuracea, Gloiocephala menieri, and Armillaria tabescens. The genera containing these latter species have been reassigned to the Physalacriaceae family; as of 2009, Index Fungorum also lists Rhodotus as belonging to the Physalacriaceae.

A 1986 paper reported that the species Pleurotus pubescens (Peck.) is equivalent to, and thus synonymous with, Rhodotus palmatus; according to this publication, another synonym is Lentinula reticeps (Murr.) Murr.

Description author: Nathan Wilson (Request Authorship Credit)

Created: 2009-06-17 07:39:49 PDT (-0700) by Nathan Wilson (nathan)
Last modified: 2010-04-14 17:58:59 PDT (-0700) by Nathan Wilson (nathan)
Viewed: 317 times, last viewed: 2017-12-06 11:05:45 PST (-0800)