Tricholoma vaccinum

Tricholoma vaccinum, commonly known as the russet scaly tricholoma, the scaly knight, or the fuzztop, is a fungus of the agaric genus Tricholoma. It produces medium-sized fruit bodies (mushrooms) that have a distinctive hairy reddish-brown cap with a shaggy margin when young. The cap, which can reach a diameter of up to 6.5 cm (2.6 in) wide, breaks up into flattened scales in maturity. It has cream-buff to pinkish gills with brown spots. Its fibrous, hollow stipe is white above and reddish brown below, and measures 4 to 7.5 cm (1.6 to 3.0 in) long. Although young fruit bodies have a partial veil, it does not leave a ring on the stipe. Widely distributed in the Northern Hemisphere, Tricholoma vaccinum is found in northern Asia, Europe and North America. The fungus grows in a mycorrhizal association with spruce or pine trees, and its mushrooms are found on the ground growing in groups or clusters in late summer and autumn. Although some consider the mushroom edible, it is of poor quality and not recommended for consumption. The ectomycorrhizae of T. vaccinum has been the subject of considerable research. The species was first described in 1774 by German mycologist Jacob Christian Schäffer as Agaricus vaccinus. According to MycoBank, synonyms include August Batsch's 1783 Agaricus rufolivescens, Jean-Baptiste Lamarck's 1783 Amanita punctata var. punctata, and Lucien Quélet's 1886 Gyrophila vaccina. Marcel Bon described the variety T. vaccinum var. fulvosquamosum in 1970, which has squamules (minute scales) arranged in a concentric fashion on the cap; Manfred Enderle published this taxon as a form in 2004. According to the infrageneric classification of Tricholoma proposed by Rolf Singer in 1986, Tricholoma vaccinum is placed in the section Imbricata, subgenus Tricholoma in the genus Tricholoma. Imbricata includes species with a dry cap cuticle, with a texture that ranges from roughened or squamulose (resembling suede) to almost smooth. The specific epithet derives from the Latin word vaccinus and means 'cow-colored'. The mushroom's common names include the 'russet scaly tricholoma', 'fuzztop', and 'scaly knight'. The cap of T. vaccinum is initially broadly conical, then convex and finally flattened; its diameter is usually between 2.5 and 6.5 cm (1.0 and 2.6 in). The cap margin is initially curved inwards, and shaggy from hanging remnants of the partial veil. The partial veil is cotton-like, and does not leave a ring on the stipe. The fibrous to scaly cap surface ranges in color from reddish-cinnamon to brownish-orange to tan. The gills have an adnate to sinuate attachment to the stipe, and are crowded closely together. There are between three and nine tiers of lamellulae—short gills that do not extend completely from the cap edge to the stipe. The gills are dingy white, and frequently stain reddish brown. The stipe is 4 to 7.5 cm (1.6 to 3.0 in) long and 1 to 2.2 cm (0.4 to 0.9 in) thick, and becomes hollow in age. It is roughly equal in width throughout its length and ranges in color from whitish to the same color as the cap, but lighter, and sometimes with reddish-brown stains; it is lighter in color near the apex. Like the cap, the stipe surface is fibrous to scaly. The odor of the fruit bodies is unpleasant. The mushrooms produce a white spore print, and the spores are broadly elliptical, smooth, hyaline (translucent), inamyloid, measuring 6–7.5 by 4–5 μm. The basidia (spore-bearing cells) are four-spored, without clamps, and measure 17–32 by 6.0–7.5 μm. The hymenium lacks cystidia. The arrangement of the hyphae in the cap cuticle ranges from a cutis (with hyphae that run parallel to the cap surface) to a trichoderm (hyphae perpendicular to the cap surface); these hyphae are roughly cylindrical, and measure 3.5–8.0 μm wide, with roughly cylindrical to club-shaped ends that are 6.0–11.0 μm wide. There are no clamp connections in the hyphae of T. vaccinum. Although the fruit bodies are considered edible, they are of low quality, and generally not recommended for consumption due to their resemblance to and potential for confusion with toxic brown Tricholomas. Orson K. Miller, Jr. considers them 'bitter and not edible'. The fruit bodies can be used to create yellow dyes to color wool or other fibers. With its reddish-brown wooly cap, white gills, and hollow stipe, Tricholoma vaccinum is a fairly distinct mushroom and is unlikely to be confused with other Tricholoma. Tricholoma imbricatum somewhat resembles T. vaccinum, but has duller brown colors, is less robust in stature, and has a solid (not hollow) stalk. Another lookalike, T. inodermeum, has a less woolly cap texture and flesh that turns bright pinkish red when injured. It associates solely with pine species and prefers calcareous soil. Other brownish Tricholoma species include T. fracticum, T. dryophilum, and T. muricatum. The scaly and fibrous cap surface of T. vaccinum might be confused with Inocybe, but species in this genus can be distinguished by their brown spore prints.