The veiled species of Hebeloma in the western United States / Alexander H. Smith, Vera Stucky Evenson, and Duane H. Mitchel.

INTRODUCTION
Fries (1821) treated Hebeloma as a Tribe ("Tribus") of Agaricus.
The first three words of his description are: "velum marginale floccosum.... " Agaricus fastibilis, the only species included, he described
as follows (as translated):... odor nauseous, taste unpleasant; stipe
1.5-3 inches long, subequal, becoming hollow; pileus firm, obtuse,
when moist slimy ("viscosus"); lamellae often with serrulate edges
bearing droplets; pileus slightly expanded, opaque; stipe squamulose,
white; spores subargillaceous. Thus H. fastibile, described as a veiled
species, became the type of the genus Hebeloma. Fries (1838) and
subsequent authors have included species with and without veils. In
general, the concept of the genus has been followed quite consistently.
As for North America, few comprehensive treatments of the genus are available. Murrill's (1917) treatment is the most extensive but
is outdated both as to the number and type of characters emphasized
in his classification. Singer (1962 and 1975) placed the genus in the
Cortinariaceae between Inocybe and Alnicola. We emphasize the relationship to Cortinarius on the basis of the microanatomy and floristic
characteristics. Romagnesi (1965), Bruchet (1970), and Bohus (1972)
published works which deal critically with taxa at the species level. We
have found, in the central Rocky Mountains of Colorado, some of the
species described by them as occurring in central Europe. The evaluation of characters used for establishing species concepts by the abovementioned authors has been most helpful to us in our study of the
species from western North America-particularly those from the central Rocky Mountains. Our study, however, has led to an "explosion"
of species in the subgenus Hebeloma. This increase in the number of
species, as presented here, mirrors the situation previously found in
other genera of the Agaricales when the flora of North America is
compared quantitatively with that of Europe. As examples we cite
Psathyrella (Smith 1972), Lactarius (Hesler and Smith 1979), Pholiota
(Smith and Hesler 1968), and Mycena (Smith 1947).
Most recent field guides and other works written for the nonspecialist offer little help in either the taxonomy or toxicology of the
genus. Smith and Weber (1980) illustrate one species in each subgenus.
Miller (1972) illustrates two species. Arora (1979) treats only one
veiled species and lists it as poisonous. He states that the presence of a
cortina distinguishes it from the common members of the genus. This
suggests that veiled species are less "common" than those lacking a