Lentinus arcularius (Batsch) Zmitr. 2010

Guidance for identification (German text)

Polyporus arculariformis Murrill, Torreya 4 : 151. 1904
Pileus circular, umbilicate, 0.6-0.8X0.05-0.1 cm.; surface regularly concentrically rugose about the white, depressed center, isabelline to avellaneous, slightly imbricat efibrillose ; margin thin, acute, soon deflexed, nearly white, changing to isabelline, beset with numerous long, white, pointed cilia : context membranous, white, perfectly opaque ; tubes 0.2-0.4 mm. long, 2-3 to a mm., radially elongate, decurrent, pallid, edges thin, irregularly toothed and fimbriate: spores hyaline, smooth, thin-walled, 2-2.5X7-8//: stipe central, stuffed, equal, concolorous, beset with sharp bristles which partially disappear with
age, densely tomentose at the base, 1.5-2 cm. long, 0.5-1 mm. thick.
Type locality : Unaka Springs, Tennessee. Habitat : Dead fallen branches in woods. Distribution : Known only from the type locality.

Polyporus arculariellus Murrill, Bull. Torrey Club 31 : 36. 1904
Favolus Curtisii Berk. Grevillea 1 : 68. 1872.
Pileus very thin, circular, umbilicate, 2X0.1 cm. ; surface smooth, orange-yellow to brown in the type specimen ; margin thin, somewhat irregular, beautifully ciliate : context pallid, membranous,' translucent ; tubes ochraceous when dry, very short, mouths large, angular, oblong, 2 to a mm., edges thin: spores not examined: stipe central, thicker
below, setulose, darker than the pileus, 2 cm. long, 2 mm. thick.
Type locality : North Carolina.
Habitat : On dead wood.
Distribution : Known only from the type locality.

Polyporus arcularius (Batsch) Fries, Syst. Myc. 1 : 342. 1821
Boletus arcularius Batsch, Klench. Fung. 97. 1783. Boletus exasperatus Schrad. Spic. Fl. Germ. 153. 1794.
Pileus circular, convex, umbilicate, 1-2.5 X 0.1-0.2 cm. ; surface azonate, concentrically
rugose when dry, fuscous-squamulose to fulvous and nearly glabrous ; margin acute, ciliate-
dentate, straight, inflexed in drying : context white, membranous ; tubes slightly decurrent,
rather firm, white to brownish, 1-2 mm. long, mouths large, oblong-rhomboid, 1-2 to a
mm., edges thin, elongate, denticulate: spores cylindrical, pointed at the ends, smooth,
thin-walled, 2-guttulate, copious, 1.5-2.5X^-8^ : stipe central, slender, even, fuscous-gray
to fulvous, subsquamulose to glabrous above, hispid-tomentose at the base, 2-4 cm. long,
2-3 mm. thick.
Type locality : Germany.
Habitat : Decaying wood of a variety of trees.
Distribution : Connecticut to Florida and west to Colorado and Mexico ; also in Europe.

Polyporus arcularius is a species of fungus in the genus Polyporus. It is also known as the spring polypore or the scientific name Lentinus arcularius. It has been found on all continents, but has primarily been documented in the United States, Austria, Mexico, Australia, and Japan. It was first documented in 1783 by German naturalist August Batsch under the name Boletus arcularius. It was later renamed to Polyporus arcularius in 1821 by Swedish mycologist Elias Magnus Fries.