Photo: © Steve Trudell
Hydnum umbilicatum
Pk.

Pileus: 1.5 - 5.0 cm broad; broadly convex to planar at first, becoming arched with maturity, developing an acute pronounced depression (umbilicate); margins inrolled when young then straight and even and finally flaring to undulating, splitting to eroded when mature; surface dry to moist, unpolished, smooth, at times mealy (with minute scales), at times lumpy and uneven; when young orange on disc fading to white to pallid on margins, when mature dark orange on disc, fading to light orange on margin, becoming darker when bruised; context 8 mm at junction of stipe, firm and soft; white at first then discolouring orange when bruised; taste mild; odour indistinct.

Spines: Horizontal to decurrent; close, soft and fleshy; white at first, becoming light orange to greyish orange when mature or bruised.

Stipe: 3 - 5 cm long X 1.0 - 1.5 cm wide at apex, 2.0 - 2.5 cm at base; equal to tapering upwards or at times tapering downwards; usually central though at times eccentric; surface, like cap, unpolished and dull, dry; white with orange tints when young, then pale to deep orange at maturity or when bruised; context solid, firm, coloured and bruised like stipe surface.

Microcharacteristics: Spore print white, spores 8 - 10 X 7 - 8 µm, globose to subglobose, smooth, inamyloid; hymenial cystidia absent.

Comments: This species was previously known as Dentinum umbilicatum. There is a less common relative of H. umbilicatum in these forests, H. repandum. They are differentiated microscopically by spore size and stature. Hydnum repandum has smaller spores and is more robust.

Further Reading:

Hall, D. and D.E. Stuntz. 1971. Pileate Hydnaceae of the Puget Sound Area. I. White spored genera: Auriscalpium, Hericium, Dentinum and Phellodon. Mycol. 63:937-1098.