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

154

North American Species of Lactarius

Observations.-Although closely related to L. ruginosus, L. fuliginellus differs in the mild taste, close gills, and lower spore ornamentation. L. fumosus var. fumosus has much narrower caulocystidia
(3-7 yu wide) and paler less robust basidiocarps. In L. fuliginosus
there is a distinct layer of inflated cells from which the turf elements
of the pileus originate. Such a layer is lacking in both L. fuliginellus
and L. fumosus. L. fuligenellus has the pattern of color change described for the typical form of L. picinus but the latter is acrid, grows
under conifers, and has lower spore ornamentation. L. fumosus var.
fumosoides has narrower caulocystidia, narrower gills, and usually
grows under conifers. The cuticle of the pileus in young pilei of L.
fuliginellus is often a dense turf of long narrow elements 30-60 X 6-10 u,
but in old pilei these elements apparently have enlarged somewhat
since many are clavate, subcapitate, or cystidioid and up to 14 /1 or
more broad.
Many of the lactifers, as revived in KOH, are yellow. This reaction should be checked on fresh material. Previously we described
macrocystidia for this species but many collections in recent years
did not show them. In a detailed restudy of the type we were able to
find instances where a spore was obviously forming on a "cystidium"
(only one sterigma present). Also we found 4-spored basidia with
spangled-refractive content. In our estimation this leaves open the
question of the presence of "macrocystidia" for this species. It is
impossible to determine if all the monosterigmate "basidia" will
actually produce spores, or, if spores do form, that they will be discharged. Under these circumstances we feel that no taxonomic significance should be attached to these structures in this species.
Material cited.-MICHIGAN: Gilliam 856 (MICH); Hoseney
2259, 2564 (all MICH); Mazzer 4066 (MICH); Patrick 2276 (MICH);
Smith, August 2, 1973, 6806, 6982, 18617, 18633, 62796, 62922, 64576
(type, MICH), 81547, 84224, 84460, 84461; OHIO: Mazzer 8878,
8917 (all KE).
35. Lactarius eburneus Thiers
Mycologia 49: 715. 1957
var. eburneus
Pileus 4.5-6.5 cm broad, plane with a shallow depression to shallowly infundibuliform, "cartridge-buff," "ivory-yellow" to "cinnamonbuff" during all stages of development, margin incurved, becoming
plane to slightly decurved, entire, surface dry, more or less even,
minutely tomentose under a lens, dull, azonate. Context thick, white,