Lilac-brown bolete

Fruit bodies have caps that are initially convex, later becoming broadly convex to more or less flat, with a diameter of 5–12 cm (2.0–4.7 in). The cap surface is dry to slightly sticky, with a texture ranging from smooth to somewhat felt-like. Its color is purplish brown to grayish brown to reddish brown; young specimens are often covered with a fine whitish bloom (a delicate, powdery coating). The flesh is whitish, and slowly stains gray-brown when it is cut or injured. It has no distinctive odor, and a mild to slightly bitter taste. On the cap underside, the pore surface is dark chocolate brown to purple brown, and stains dark brown where bruised. The nearly circular pores number up to 3 per millimeter, and the tubes are 0.9–2.2 cm (0.4–0.9 in) deep. The solid stipe measures 4.5–9 cm (1.8–3.5 in) long by 1–4 cm (0.4–1.6 in) thick. Its color is similar to that of the cap, and it has a scurfy surface from a dense coating of purplish to purple-brown scabers. The lilac-brown bolete produces a pinkish to reddish-brown to amber-brown spore print. The smooth, translucent spores are narrowly spindle shaped and measure 11–17 by 3.5–5 μm. Collections made in Costa Rica have shorter spores (10.5–13.3 μm) and smaller fruitbodies than eastern North American material; Guyanese material also has smaller spores, measuring 9.7–12 μm. These differences are attributed to clinal variation. …

Fruit bodies of Sutorius eximius grow in the soil singly or scattered among leaf litter. A mycorrhizal species, the bolete has been recorded growing in association with plants from various genera, including Dicymbe, Dipterocarpus, Fagus, Hopea, Quercus, Shorea, and Tsuga. The species has been recorded from North America (in the east from June to September), Costa Rica, and Indonesia. In Costa Rica, where it usually associates with the endemic oaks Quercus seemannii and Q. copeyensis, the lilac-brown bolete can be locally abundant in the Cordillera Central and the Cordillera de Talamanca. Additional locations with collections that have not been confirmed by DNA analysis include Guyana, Japan, China. Although S. eximius has been reported from Thailand, molecular analysis of Thai collections suggests that they represent a distinct, as-yet unnamed species.

Sutorius eximius is typically considered an edible mushroom, and listed as so in several North American field guides. Charles McIlvaine and Louis Krieger both wrote favorably of the bolete, but a series of gastroenteritis-like poisonings reported from both Canada and New England have cast doubt on potential edibility. According to Greg Marley, author Roger Phillips was the first to include a toxicity warning in his 1991 book Mushrooms of North America. Despite this, the lilac-brown bolete remains one of the most common mushrooms eaten by people living in the Hengduan Mountains region of southwestern China.