The Waxy Caps: Hygrophorus and Hygrocybe

[ Basidiomycetes > Agaricales > Tricholomataceae . . . ]

by Michael Kuo

The waxy caps are white-spored mushrooms with thick, waxy gills and, frequently, waxy or slimy caps. Two main groups of waxy caps can easily be distinguished in the field: those that tend to have medium-sized to large caps that are convex, slimy, and dull-colored or whitish; and those those that have smaller caps that are convex to conical, slimy or dry, and often brightly colored. These groups correspond roughly to the genera Hygrophorus and Hygrocybe (in that order), though many waxy caps can be found that require the use of a microscope in order to be certain which genus applies. Species of Hygrophorus have divergent gill tissue, while species of Hygrocybe demonstrate parallel gill tissue. A third group, sometimes separated in the genus "Camarophyllus," has interwoven gill tissue.

Some field guides treat all the waxy caps as species of "Hygrophorus," but DNA evidence has upheld the partition between the mycorrhizal genus Hygrophorus and the saprobic genus Hygrocybe (see Moncalvo et al., 2002). That's the good news, if you are a traditional morphologist. The bad news is, the waxy caps are scattered in and among the omphalinoid mushrooms, along with some species of Clitocybe, and the well known Hygrophorus/Camarophyllus pratensis may not even belong in the group. See the Omphalinoid/Hygrophoroid Clade for further information.

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Identification of waxy caps ranges from easy to extremely difficult. Some, like the blackening and brilliantly scarlet Hygrocybe conica, are immediately recognizable and distinct. On the other end of the spectrum, there are seemingly dozens of whitish species separated on the basis of erudite microscopic features. Hesler & Smith's 1963 monograph of the waxy caps recognizes 244 species in North America, and there is no more recent comprehensive treatment for the entire continent--though treatises for California (Largent, 1985), Nova Scotia (Bird & Grund, 1979), and the Pacific Northwest (Stuntz, 1975) have been developed. In addition, David Boertmann's recent treatment (2000) of the genus Hygrocybe in northern Europe contains many species which are also found in North America. None of these treatments is supported by DNA evidence, however, and the mycological world awaits a study of the waxy caps that is based on more than their physical features.

Species Pages

References

Arora, D. (1986). Mushrooms demystified: A comprehensive guide to the fleshy fungi. Berkeley: Ten Speed Press. 959 pp.

Bird, C. J. & Grund, D. W. (1979). Nova Scotian species of Hygrophorus. Proceedings of the Nova Scotia Institute of Science 29: 1-131.

Boertmann, D. (2000). The Genus Hygrocybe. Denmark: Danish Mycological Society. 184 pp.

Cantrell, S. A. & Lodge, D. J. (2004). Hygrophoraceae (Agaricales) of the Greater Antilles: Hygrocybe subgenus Pseudohygrocybe sections Coccineae and Neohygrocybe. Mycological Research 108: 1301-1314.

Cibula, W. G. & Weber, N. S. (1996). Hygrocybe andersonii a new psammophilus Hygrocybe from Horn Island, a Mississippi barrier island. Mycologia 88: 544-546.

Hesler, L. R. and Smith, A. H. (1963). North American Species of Hygrophorus. Knoxville: U Tennessee P. 416 pp.

Kauffman, C.H. (1918). The gilled mushrooms (Agaricaceae) of Michigan and the Great Lakes region, Volumes I and II. New York: Dover. 924 pp. (1971 Reprint.)

Largent, D. L. (1985). The Agaricales (Gilled Fungi) of California. 5. Hygrophoraceae. Eureka, California: Mad River Press. 208 pp.

Larsson, E. & Jacobsson, S. (2004). Controversy over Hygrophorus costa settled using ITS sequence data from 200 year-old type material. Mycological Research 108: 781-786.

Miller, O. K. Jr. (1984). A new species of Hygrophorus from North America. Mycologia 76: 816-819.

Mitchell, D. H. & Smith, A. H. (1975). Notes on Colorado fungi I. Hygrophorus amarus. Mycologia 67: 672-674.

Smith, A. H., Smith, H. V. & Weber, N. S. (1979). How to know the gilled mushrooms. Dubuque, Iowa: Wm. C. Brown. 334 pp.

Stuntz, D. E. (1975). Trial field key to the species of Hygrophorus in the Pacific Northwest. Retrieved from the Pacific Northwest Key Council Web site: http://www.svims.ca/council/Hygrop.htm

Wood, W. F. et al. (2003). Indole and 3-chloroindole: The source of the disagreeable odor of Hygrophorus paupertinus. Mycologia 95: 807-808.

Cite this page as:

Kuo, M. (2007, January). Waxy caps: Hygrophorus and Hygrocybe. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/hygrophoraceae.html