Photos: © Sharmin Gamiet
Steve Trudell
Boletus mirabilis
Murr

Pileus: 3.5 cm - 14.0 cm broad; convex when young becoming plano-convex when mature; margins inrolled at first, then straight and even when mature, at times with flaps of tissue exceeding the tubes; surface dry to moist, rough with appressed fibrils at first then becoming scaly and finally squarrose when mature, often areolate, appearing roughened like stiff velvet; colour evenly vinaceous, dark to reddish violet brown when young, fading to brown to dark brown with age; context 1 - 1.5 cm at junction of stipe, thick, firm, white to pale to pastel yellow, sometimes staining vinaceous brown when bruised; taste mild; odour indistinct.

Tubes: Ascending at first, then notched with a depression appearing free around the stipe; pores are large, 1 mm wide, round to angular especially towards the stipe, greyish yellow to yellowish white, not changing or at times becoming deeper yellow when bruised.

Stipe: 9 - 12 cm X 0.5 - 1.0 cm wide at apex, 1.5 - 4.0 cm wide at base; bulbous at first then becoming equal to tapering upwards to club shaped when mature; surface dry, with long grooves or ridges (striations), at times the apex with reticulations, but soon disappearing, with yellow mycelium at base; dark to reddish brown, often streaked with darker brown black; context firm, solid, colour pallid to pale to pastel yellow with greyish red streaks.

Microcharacteristics: Spore print olive brown; 19 - 25 X 5 - 12 µm, ellipsoid to spindle shaped; abundant and prominent, hour glass to fusoid ventricose shaped, hymenial cystidia present.

Comments: This species is a common and abundant species in these forests. It is a western hemlock associate, found throughout the Pacific Northwest. It is often found on, though not confined to, coarse woody debris. It is separated from the other 2 boletes in these forests by not changing blue when bruised and having a mild taste. Boletus coniferarum turns blue when bruised and has a very bitter taste. Boletus edulis is separated from B. mirabilis by the colour and texture of the pileus, tubes and stipe.

Further Reading:

Arora, D. 1986. Mushrooms Demystified. Ten Speed Press. Berkeley, Ca. pp 958.

Thiers, H.D. 1975. California Mushrooms: A field guide to the Boletes. Hafner Press. pp.261.