Russula decolorans var. rubriceps Kauffman, Rep.

Adamčík, Slavomír, Jančovičová, Soňa & Buyck, Bart, 2015, Type-studies in American Russula subsection Decolorantes (Russulales, Basidiomycota), part II., Phytotaxa 231 (3), pp. 245-259 : 249-252

Russula decolorans var. rubriceps Kauffman, Rep. Michigan Acad. Sci. 13: 220. 1911. Figs. 10–18

≡ Russula rubriceps (Kauffman) Singer, Mycologia 35: 151. 1943.

Original description:— The shape of the young and old pileus is well represented in Cooke’s figure of R. decolorans, Plate 1079 . The color of the pileus is, however, rubber-red (Sacc. colors) and persistent, changing only in age or on drying as a result of the cinerescent flesh. The pellicle is adnate, scarcely separable except on the margin, vanishing on the disk and sometimes ochraceous spotted where the pellicle has disappeared. It is firm and the margin in not striate or very slightly so in age. These characters ally it to the Rigidae. It is slightly viscid. Flesh is firm, white, tinged ashy in age, becoming dark cinereous on the stem where bruised. The taste is mild and when fresh was taken for R. lepida . Spores creamy-white in mass. It is smaller, apparently, at least in our specimens, than the type. It is possible that it is a var. of R. depallens Fr. , but that species is not well understood even in Europe.

On the ground in beech and white pine woods. New Richmont, Allegan Co., Sept. Apparently rare.

The scarlet or vermillion pileus, cinerescent flesh, mild taste, creamy-white spores and firm consistency are the distinguishing marks. The margin of the pileus is straight at first and the gills are broadest in front.

Spores subglobose, (6.6–)6.9–7.8(–8.2) × (5.5–)5.8–6.6(–7) μm, average 7.3 × 6.2 μm, Q=(1.09–)1.13–1.24(–1.35), average Q=1.19, ornamentation composed of moderately numerous [4–7 spines in a 3 μm diam. circle] spines measuring 0.8–0.9 μm high, occasionally interconnected [0–2(–3) line connections in the circle], or frequently fused in pairs or short chains [0–3(–4) fusions in the circle], rarely isolated; suprahilar plage distinct, amyloid although often partly. Basidia 40–49 × 10–12.5(–13.5) μm, average 44 × 11.5 μm, 4-spored, clavate-pedicellate; basidioles first cylindrical, then narrowly clavate. Subhymenium pseudoparenchymatic. Lamella trama mainly composed of sphaerocytes. Hymenial cystidia numerous [ca. 2200/mm 2], measuring (51–)59–80(–90) × 8.5–11.5 μm, average 70 × 10 μm on gill faces, smaller near the gill edge, fusiform or rarely clavate, pedicellate, neither mucronate nor appendiculate, thin-walled, sometimes with slightly to distinctly thickened walls (0.5–1 μm) on gill faces, for the larger part filled with heteromorphous contents. Marginal cells poorly differentiated and mixed with numerous cheilocystidia, some with few inclusions, 19–35(–44) × 6–9(–11.5) μm, average 28 × 7.5 μm. Pileipellis orthochromatic in Cresyl Blue, not sharply delimited from the underlying sphaerocytes of the context, vaguely divided in a loose, 50–60 μm deep and strongly gelatinized suprapellis of erect hyphal ends and pileocystidia, gradually passing into a dense, 30–40 μm deep and less gelatinized subpellis of more intricate and irregularly oriented hyphae that are ca. 2–3.5 μm wide. Acidoresistant incrustations not observed. Terminal cells near the cap margin measuring (16–)22.5–35(–42) × 2–3 μm, average 29 × 2.5 μm, slender, moniliform, obtuse or slightly narrowed towards tips, embedded in gelatinous matrix, in cap centre more flexuous and more densely arranged, measuring (19–)26.5–40(–53) × 2–3.5 μm, average 33 × 3 μm, sometimes mucronate; subterminal cells equally wide, mostly irregular-nodulose, branched and intricate, descending in a very dense subpellis. Pileocystidia one- to three-celled, with terminal cells measuring (24–)26–57(–77) × (3.5–)4–7(–8.5) μm, average 41 × 5.5 μm, cylindrical or narrowly clavate, longer ones originating deep in subpellis, in Congo Red with heteromorphous, banded or crystalline content, hardly graying in sulfovanillin, thin-walled, continuing as cystidioid hyphae also in deeper cap trama. Clamp connections absent in all parts.

Examined material:— UNITED STATES. Michigan. Allegan Co., New Richmond, C.H. Kauffman (MICH 12202, holotype).

Commentary:— We agree with Singer (1943) that Kauffman’s variety is sufficiently different from the European R. decolorans to be recombined at species level: R. rubriceps (Kauffman) Singer. However , this taxon is very close to R. rubescens Beardslee , see below.

Figures

FIGURES 10–12. Russula delolorans var. rubriceps (holotype). 10. Pileocystidia near the cap margin (right) and near the cap centre (left). 11. Hyphal extremities in the cap center. 12. Hyphal extremities near the cap margin. Contents of cystidia are represented as observed in Congo Red for some elements only, the others are simply filled with dots to indicate their cystidial nature. Scale bar equals 10 μm. Drawings by S. Jančovičová.

FIGURES 13–18. Russula delolorans var. rubriceps (holotype). 13. Basidia. 14. Basidioles. 15. Marginal cells. 16. Basidiospores in Melzer’s reagent. 17. Cheilocystidia. 18. Pleurocystidia. Contents of cystidia are represented as observed in Congo Red. Scale bar equals 10 μm, but only 5 μm for spores. Drawings by S. Jančovičová.