Hydnum geminum Swenie & Matheny

Swenie, Rachel A., Baroni, Timothy J. & Matheny, P. Brandon, 2018, Six new species and reports of Hydnum (Cantharellales) from eastern North America, MycoKeys 42, pp. 35-72 : 35

Hydnum geminum Swenie & Matheny nom. nov. Fig. 7

≡ Hydnum caespitosum Banning ex Peck, Rep. N.Y. St. Mus. 44: 74 (1891), non Valenti (1868)

Type.

UNITED STATES. Maryland: Carroll County, in clusters at the roots of trees and near old stumps, Aug-Sep, ca. 1880, M.E. Banning (holotype: NYS-F-3506).

Etymology.

geminum (L.), twin, in reference to the clustered habit

Description.

Pileus up to 40 mm wide, subconfluent, convex to expanded or subplane, subregular; surface appressed-fibrous, pale ochre, yellow, or dark flesh-colored. Spines short (<3 mm long), conical, acute, decurrent, pale ochre or light flesh color. Stipe up to 60 × 10 mm, united at the base, subcylindrical, subflexuous, floccose above, subglabrous below, whitish, staining yellow where bruised, solid. Context fleshy, white, turning yellow where cut. Taste mild.

Basidiospores 6 –6.4– 7 μm × 4.5 –5.2– 6 μm, Q=1.09 –1.24– 1.36 (n=12/1), broadly elliptic to subglobose, smooth, thin-walled, hyaline in KOH. Basidia not reviving, with 4-5 sterigmata. Pileipellis not observed. Clamp connections present.

Distribution.

Eastern U.S. - Maryland (type).

Ecology.

In clusters at the roots of trees and near old stumps, August to September.

Discussion.

The new binomial H. geminum is introduced to replace the illegitimate name H. caespitosum Banning ex Peck, which is a later homonym of H. caespitosum Valenti. The gross morphological description here is reproduced from Banker (1906) after reformatting for style, and measurements appear to be based on dried specimens. Peck’s protologue, Banning’s painting, and Banker’s notes depict a species best characterized by the overall yellowish color, short decurrent spines, flavescent or yellowing flesh, mild taste, and broadly elliptic to subglobose basidiospores that are mostly 6.5 × 5 μm in size. Although specimens of H. subconnatum (described above) may share the similar caespitose or clustered habit, it differs from H. geminum by the peach-orange to dark orange-brown pileus, longer non-decurrent spines, and a stipe that bruises orange-brown, not yellow. In addition, the basidiospores of H. subconnatum are larger than in H. geminum - 8.5-9.5 × 7.5-9 μm. Basidiomes of H. subtilior sometimes have an overall pale yellow tone and stain when bruised or cut in half, but basidiospores are smaller in H. geminum , and the overall basidiome stature of the holotype appears much stouter than in the generally slender H. subtilior .

Upon examining the holotype of H. caespitosum , we found that basidiomes had very short spines (<1 mm) with very few spores and basidia. This aligns with Peck’s notes indicating he did not obtain spores and suggests the holotype consists of immature basidiomes.

We have not yet recorded H. geminum in eastern North America. Banker (1906) refers to a collection made by Earle from Connecticut now housed at NCU (NCU-F-0012251). We have not re-examined this collection, but Banker describes it as somewhat darker than the type.