Suillus placidus
Description
Suillus Pacidus is a species of fungus in the genus Suillus. It is an edible pored mushroom found in European and North American coniferous forests, growing in association with several species of pine of the subgenus Strobus. S. placidus is reportedly edible, but of mediocre quality.
This easily identified Suillus features a bald white cap and a slender stem that develops conspicuous glandular dots and smears that contrast with the stem surface. It is exclusively associated with eastern white pine, and can be found throughout the range of the host tree (northeastern North America, south through the Appalachians).
In culture, it prefers the use of nitrates as a nitrogen source that puts it into the ‘nitrate fungus’ category. Suillin, a compound made by Suillus species, and specifically from S. placidus, can induce apoptosis (programmed cell-death) in human liver cancer cells (Liu et al. 2009).
Boletus albus Peck (1872) is probably the same mushroom, according to Snell (1933, 1970).
Common names: White Suillus.
Mushroom Identification
Ecology
Mycorrhizal with Pinus strobus (eastern white pine); growing alone, scattered, or gregariously; summer and fall; fairly widely distributed in northeastern North America, west to the Dakotas and southward with the Appalachian; also found in Europe where Pinus strobus has been introduced.
Cap
4-9 cm; convex becoming broadly convex or nearly flat; sticky when fresh; white when young, darkening slightly with maturity to yellowish-white or nearly yellowish; bald or nearly so; in age, the gluten sometimes drying brownish.
Pore Surface
White when very young, becoming dull yellow; not bruising; pores becoming angular, about 1-2 per mm; tubes to 1 cm deep.
Stem
4-9 cm long; 5-12 mm thick; more or less equal above a somewhat tapered base; sticky when fresh; whitish underneath conspicuous, large glandular dots and smears that are initially pinkish but soon darken to reddish-brown or brown; without a ring; basal mycelium white.
Flesh
Whitish to yellowish; often staining slowly pinkish to reddish when sliced, especially in the stem base.
Chemical Reactions
Ammonia on cap surface pink, then black to dull red or purple; on flesh pink to red, becoming purplish or grayish. KOH on cap surface pink, becoming black or purple; on flesh pink.
Spore Print
Cinnamon brown.
Microscopic Features
Spores 7-9 x 2-3 µ; smooth; subfusiform; hyaline to yellowish in KOH. Pleurocystidia cylindric to clavate; to about 65 µ long. Cheilocystidia conspicuous; bundled; to about 80 x 8 µ; clavate to capitate; smooth or sometimes somewhat encrusted near the base; pinkish-red to reddish-brown in KOH. Caulocystidia capitate to swollen-capitate. Pileipellis an ixocutis.
Look-Alikes
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Is a Larch associate, typically darker and with a membranous stem ring.
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A rare bolete found under birch is pure white when young but develops a blue tinge as it matures. When cut, the flesh at the base of the stem turns blue-green.
History
When in 1861 German naturalist Hermann Friedrich Bonorden (1801 - 1884) described this boletoid fungus he gave it the scientific name Boletus placidus. In 1945 German-born mycologist Rolf Singer, who worked mainly in North America, transferred this species to its present genus, whereupon its currently-accepted scientific name Suillus placidus was established.
Synonyms of Suillus placidus include Boletus placidus Bonord., Gyrodon placidus (Bonord.) Fr., and Ixocomus placidus (Bonord.) E.-J. Gilbert.
Suillus, the generic name, means of pigs (swine) and is a reference to the greasy nature of the caps of fungi in this genus. The specific epithet placidus means mild or gentle - referring to appearance rather than behavior.
Photo sources:
Photo 1 - Author: Gerhard Koller (Gerhard) (CC BY-SA 3.0)
Photo 2 - Author: Suillus_placidus_97717.jpg: (CC BY-SA 3.0)
Photo 3 - Author: Suillus_placidus_97717.jpg: (CC BY-SA 3.0)
Photo 4 - Author: Jason Hollinger (jason) (CC BY-SA 3.0)
