Lactifluus rupestris
Lactifluus rupestris is a species of mushroom in the family Russulaceae. Described as a new species in 2010, it is known only from the semi-arid region in the National Park of Catimbau of Brazil. The mushroom is characterized by a stout fruit body with a smooth and sticky orange cap up to in diameter. The gills on the underside of the cap are closely spaced and frequently anastomosed. The stem is long by thick. The mushrooms exude a sparse cream-colored latex when cut or injured.
Discovery and classification
The species was found in the Brazilian semi-arid region in the National Park of Catimbau, in July 2007. It was described as new to science in a 2010 Mycotaxon publication by Felipe Wartchow of the Universidade Federal de Pernambuco. The epithet rupestris refers to the campos rupestres montane savanna—the ecoregion where the type species was collected.The authors note that the fungus does not readily fit into any of the infrageneric classification schemes outlined by previous authorities. For example, although L. rupestris has several characteristics that make the section Edules proposed by Annemieke Verbeken a somewhat close match, the taxon cannot be included because the surface of its cap is neither sufficiently areolate nor dry enough, and its spores are excessively ornamented in comparison.
Description
The cap of L. rupestris is, concave to somewhat funnel-shaped, with a central depression. Its color is orange at the center to brownish-orange towards the margin. The cap surface is somewhat sticky, and the texture is either smooth to slightly cracked. It has an indistinct layer of matted mycelial "hairs". The margin lacks striations and grooves, and is curled inward slightly. The gills are slightly decurrent, cream-salmon in color, and crowded closely together. They are up to broad and are frequently branched. The gill edges are smooth, and the same color as the gill face. There are several tiers of lamellulae interspersed between the gills. The stem is long by thick, centrally attached to the stem, cylindrical, and tapers slightly near the base. It is pale ochraceous-salmon, and slight longitudinal ribs can be seen with a magnifying glass. The flesh is spongy, pale yellow-ochre in the cap, and cream-yellow in the stem. The latex is cream-colored to roughly the same color as the gills, and not abundant.Microscopic characteristics
The spores are roughly ellipsoid to roughly spherical, and typically measure 7–8.5 by 6–7 μm. The ornamentation on the spore surface is amyloid and finely wart-like, with each wart ranging to 0.5–0.7 μm high. The warts are interconnected by thin ridges, but the ridges do not form a complete reticulum. The hilar appendage ranges in shape from narrowly obtuse to somewhat conical; the plage is not very distinct, but has an amyloid spot. The basidia are 35–50 by 8–11 μm, club-shaped, and bear mainly four, but sometimes two long sterigmata.Pseudopleurocystidia are very scarce on the gill faces; when present, they are thin-walled, 170 μm long by 24 μm wide, with brownish refractive contents, and arise from deep in the tissue of the hymenophore. The edge of the gill is sterile, and has marginal cells that are 30–45 by 4–6 μm, cylindrical to somewhat sinuous, thin-walled, and hyaline. The tissue of the cap has abundant sphaerocysts and measure 25–65 by 24–50 μm, in addition to filamentous hyphae that are up to 10 μm wide. Lactiferous hyphae are common in the cap tissue. They are up to 15 μm wide with a longitudinal orientation. Although they diverge from the trama somewhat, they do not form projecting pseudocystidia. The subhymenium is made of club-shaped to nearly spherical cells that are 16–27 by 9–17 μm. The tissue that comprises the hymenophore is made of several parts. It contains abundant, nearly isodiametric cells, and filamentous hyphae that measure 3.5–6.5 μm; lactiferous hyphae are frequent, up to 7–12 μm wide, straight and only occasionally branching. The cap cuticle is a trichoderm—meaning the outermost hyphae emerge roughly parallel, like hairs, perpendicular to the cap surface. It is up to 140 μm thick and comprises two layers. The upper layer, the suprapellis, is made of plentiful, colorless hyphae that are 20–51 by 4–6 μm, thin-walled, and range in shape from obtuse to somewhat acute to knob-like or pear-shaped. The lower layer of the cap cuticle, the subpellis, is made of both plentiful hyphae that are 3–8 μm wide and somewhat more inflated colorless cells up to 10–18 μm wide. Lactifluus rupestris does not have clamp connections in its hyphae.