North American species of Lactarius / L. R. Hesler, Alexander H. Smith.

PREFACE
In numbers of North American species, Lactarius is a large
genus. Recent increased attention to the agarics, however, has not
brought forth a satisfactory manual for the identification of its taxa.
Collectors of this group have, therefore, been frustrated by an inability
to name with accuracy many of their collections; and when they have
turned to the specialist, many collections have gone unnamed.
The only attempt to contribute to the solution of this problem is
that of Burlingham, in her two accounts published more than sixty
years ago (Burlingham 1908, 1910b). Her monographs are historically
valuable and have served rather well for the eastern United States,
but are incomplete for other sections of this continent. Her second
account (1910b) includes a key to seventeen groups and a key to and
descriptions of species known to her under each. The seventy-two
species contained in her monograph represent a small fraction of the
number we now recognize for North America. Our longer list has
been made possible by accelerated field work, not only by us, but
also by numerous collectors over North America, and by our effort to
employ such critical taxonomic methods as seemed promising.
For our purposes the history of the genus Lactarius may be said
to begin with the publication of Systema Mycologicum, volume 1, in
1821, by Elias Fries. This work has been selected as the starting point
for the nomenclature of the fleshy fungi generally but excluding the
Gasteromycetes. It has been legislated (Stafleu et al. 1972) that the
publication date of all three volumes of the Systema shall be set at
January 1, 1821. Thus any other works appearing with an 1821 date
line are "post-Friesian." Fries (1821) proposed the tribe Galorrheus as
a "Tribe" of Agaricus. That same year S. F. Gray published Lactarius
as a genus and included a substantial number of species which are
today still classified under that name. Since 1821 a number of names
now regarded as synonyms of Lactarius have been proposed, but the
concept of the genus and its name have remarkable continuity from
1821 to the present.
There are, however, three schools of opinion on the species to be
selected as the type for the genus. Donk (1962) preferred L. piperatus
for Lactaria Persoon, which genus he equated with Lactarius (D. C.)
S. F. Gray. The above species was included by Fries in his work of
1821, but very near the end and under a division "Proprii" which
he later abandoned. Singer (1962, 1975) prefers L. torminosus. We