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

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North American Species of Lactarius

study, that a host of additional "one-character variants" will be found
throughout the genus here in North America. The species of subgenus
Tristes are often abundant and feature large basidiocarps, and it is
hoped that our study will stimulate studies of their chemical constituents. Such studies should be carried out in conjunction with critical
taxonomic studies to determine in detail the pattern of distribution of
compounds that might affect the use of these mushrooms as human
food. Critical studies cannot be made on most herbarium specimens
at present because the necessary data were not recorded at the time
the collections were made and are now not recoverable.
KEY TO SECTIONS
1. Basidiocarps white to lilac-drab, umber or generally umber-brown; wounds
of lamellae soon staining pinkish lilac, lilac, violet, or brownish violaceous;
pileus typically viscid when fresh............ Section Violaceo-Maculati (p. 322)
1. Latex not staining gills as in above choice............................... 2
2. Pileus and stipe distinctly viscid on fresh young basidiocarps (or under
the microscope a slime layer present on both the pileus and at the midportion of the stipe)................... Section Pseudomyxacium (p. 342)
2. Stipe moist to dry but not viscid................................... 3
3. Pileus viscid, subviscid or glabrous and lubricous but not appearing fibrillose
or squamulose when faded; stipe dry (lacking either a cuticle of gelatinized
hyphae or one showing slime in the cuticular layer)...... Section Tristes (p. 372)
3. Neither pileus nor stipe viscid; pileus typically fibrillose, scurfy or squamulose, or glabrous and dry......................... Section Colorati (p. 398)
Section VIOLACEO-MACULATI sect. nov.
Pileus glutinosus, viscidus, udus vel siccus; latex albus vel subalbidus, demum lilacinus vel violaceus; lamellae demum ~ violaceomaculatae.
Typus: Lactarius subpalustris
Observations.-The species of this section are often grouped with
those having yellow pilei but similar staining reactions on the lamellae.
These to us seem to be more closely related to L. scrobiculatus in
subgenus Piperites.
One of the interesting features of some species (e.g., L. uvidus)
in the section is the green reaction of 2.5 percent KOH on the cuticle
of the pileus. It is obvious to us from collections by Wells and Kempton
in Alaska, that L. uvidus and related variants in that state would make
an interesting study. We suspect most of the species in the section to
be associated with broad-leaved trees (hardwoods), but L. pallescens, at
least, is clearly an exception.