Hydnum repandum Linnaeus

Figure 1 Hydnum repandum (PLP847_2018_184) growing gregariously in Michigan hardwood forest (A). The cap is orange and broadly (2-17 cm) convex to plane with a depression in the middle, margin is undulate (B). Flesh is thick, firm, brittle and white but bruising dark orange (C). This fungus is referred to as the “hedgehog mushroom” because of the teeth on the underside of the cap (D).

Hydnum repandum Linnaeus is a widely distributed mycorrhiza associated with hardwoods or conifers. Also known as the “hedgehog mushroom” the genus is grouped, despite being toothed, with the Cantharellales and likewise it is a choice edible. Mature fruiting bodies (summer and fall) appear alone or in clumps and produce dull to pale orange caps (Figure 1-A, 1-B) with small spines or teeth on the underside of pilei (Figure 1-D). The cap texture is glabrous and dry, shape is broadly (2-17 cm) convex to plane with a depression in the middle, margin is undulate and pileipellis bruises a darker shade of orange. Spines (2-7 mm long) are white to pale to dull orange and decurrent. Spores (6.5-9 x 5.5-8 µm) white (spore print), smooth and elliptical to subglobose. The stalk (3-10 cm long) texture is smooth or downy at base, shape is equal, enlarged below, or tapered downward and attachment to cap is central or eccentric. Flesh is thick, firm, brittle and white but bruising dark orange (Figure 1-C).

The ‘Father of Taxonomy’, Carl Linnaeus. Image: http://www.ucmp.berkeley.edu/history/linnaeus.html

Other comments: The genus Hydnum was originally proposed by the ‘Father of Taxonomy’ himself, Carl Linnaeus, in 1753 and Linnaeus is also attributed with naming the species repandum (same year). With more than 260 years for taxonomist to debate the classification H. repandum one might imagine phylogenetic changes occurred along the way. A recent, three-gene molecular analysis suggests that global repandum-clade may exist that is comprised of four species with potentially two different species occurring in the U.S.

Taxonomy:
Basidiomycota , Agaricomycetes, Cantharlellales, Hydnaceae, Hydnum, repandum
Reference: 
Syn = Dentinum repandum Gray
Linnaeus, C. 1753. Species Plantarum. Laurentius Salvius.
Feng, B., Wang, X. H., Ratkowsky, D., Gates, G., Lee, S. S., Grebenc, T., & Yang, Z. L. 2016.Multilocus phylogenetic analyses reveal unexpected abundant diversity and significant disjunct distribution pattern of the Hedgehog Mushrooms (Hydnum L.). Scientific reports, 6, 25586.
11.18.18

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