The Genus Hypholoma
[ Basidiomycota > Agaricales > Strophariaceae . . . ]
by Michael Kuo
The genus Hypholoma has always been hard to define with precision, even before DNA studies, but most mycologists seem to agree that a dark brown to purple-brown spore print, the absence of prominent veil remnants (other than an occasional cortina or a few wisps of tissue on the cap margin), smooth spores, and the presence of chrysocystidia (sterile cells on the gills that contain refractive, yellowish contents) are among the key characters.
Two groups of species, very different in their ecology and appearance, make up Hypholoma. The first group contains a handful of well known, medium-sized species that grow in clusters on deadwood; Hypholoma fasciculare may be the most widely distributed and common of these species. The second group contains small (sometimes very small), hard-to-identify species that grow alone, scattered, or gregariously, primarily in moss or muck, especially in sphagnum bogs or cold conifer bogs. Members of the second group, especially, are constantly shifted around between Hypholoma, Psilocybe, Pholiota, and other genera (including the newly erected "Bogbodia").
Identification of Hypholoma species in the first group, the larger wood rotters, is a matter of careful observation of macroscopic features--although the lines between the species do seem to become blurred in many collections. Identification of the little guys in muck and moss, however, should be left to those who enjoy working with microscopes; spore and cystidium morphology are used to separate the species, which all look pretty much the same to the naked eye.
If you have an older field guide that places species of Hypholoma in the genus Naematoloma and you're wondering, "Why did Naematoloma get the works?" Well, that's nobody's business but the Turks.