Russula purpureotincta R.F.R. McNabb

Egon, Bart Buyck, Jerry, Egon Horak, Cooper, Jerry A. & Song, Yu, 2024, Russula (Basidiomycota, Russulales, Russulaceae) subsection Roseinae “ down under ”, Cryptogamie, Mycologie 20 (9), pp. 101-126 : 119-120

Russula purpureotincta R.F.R. McNabb

( Figs 15-18 )

New Zealand Journal of Botany 11: 711 ( McNabb 1973).

TYPE MATERIAL. — New Zealand • Prov. Nelson, Springs Junction, Upper Grey, among Sphagnum under Nothofagus [ Fuscospora ] solandri var. cliffortioides and Nothofagus [ Lophozonia ] menziesii; 25.II.1968; E. Horak; ZT 68-086 • Prov. Nelson, W of Tophonse Saddle, at the border of a swampy locality between moss (not Sphagnum ) under Nothofagus [ Fuscospora ] solandri var. cliffortioides and Nothofagus [ Lophozonia ] menziesii; 3.III.1968; E. Horak; ZT 68-105.

PILEUS

Up to 75 mm diam., at first convex, becoming slightly depressed in the center with age, near the margin smooth to shortly striate; surface dull, when humid weakly viscid, at first reddish lilac to purplish, but rapidly discolouring, particularly between the center and the very margin, and then becoming beige-brownish-pinkish to flesh-coloured, pileipellis separable up to mid-radius.

Stipe

36-80× 10-19 mm, cylindrical or slightly narrowing towards apex, entirely white, smooth or finely striate lengthwise.

Lamellae

Equal in length or with rare lamellulae, 4-6 mm wide, normally spaced (c. 1L/mm at the pileus margin), white, becoming cream with age, not anastomosing in the dorsal interspaces, obtusely rounded at the pileus margin; gill edge smooth, concolourous.

Context

Brittle, spongy, white, unchanging on exposure. Odour not distinctive. Taste mild.

Spore print

White.

Spores

(8.13-)8.32-8.74-8.93-9.43(-10.21)×(6.67-)6.99-7.28-7.29- 7.57(-7.92) µm, Q =(1.11-)1.14-1.20-1.23-1.28(-1.34), large, subglobose to broadly ellipsoid, densely ornamented with strongly to partly amyloid spines or cylindrical warts, these up to 2 µm high in many spores and frequently curved, often in pairs, with few smaller granular warts and rare interconnecting fine lines; suprahilar spot distinctly amyloid.

Basidia

40-48×12-15µ m, clavate, 4-spored; sterigmata stout, mostly 7-8×2-3 µ m.

Hymenial gloeocystidia

Mostly 70-90×12-15 µm, abundant, on lamellar sides clavate to fusiform, thin- to slightly thick-walled; near lamellar edges distinctly thick-walled (up to 2-3 µm thick in middle portion) and smaller, mostly 40-60× 7-12µm, rarely with an additional septum in the upper part.

Marginal cells

Not differentiated.

Pileipellis

Two-layered. The suprapellis is forming at the pileus surface a trichodermal structure of densely packed, narrow and thin-walled, ascending hyphal extremities composed of 3-6 short cells which originate from a more disorganized pseudoparenchyma that constitutes its lower part; this 80-90 µm deep pseudoparenchyma is composed of strongly inflated, sausage-like, ellipsoid or spherical cells up to 30 µm diam., without zebroid incrustations on the cell walls; terminal cells of the trichoderma in the pileus center short to very short, rarely exceeding 20× 3-5 µm, either narrowing in the upper part or clavate, often slightly undulate in outline, toward the pileus margin more irregular in outline and very frequently globose to moniliform at apex. Typical pileocystidia absent. Primordial hyphae emerging from the surface of the suprapellis, slightly more voluminous than the other hyphal extremities and composed of 3-6, thin-walled cells, usually more strongly septate in the pileus center; cells shortly cylindrical to barrel-shaped, up to 8 µm diam., mostly also containing distinctly refringent, granular contents in the one or two upper cells; their terminal cell frequently up to 35 µm long, more regular in outline compared to the other sometimes subcapitate hyphal extremities; subpellis ill-defined. Cystidioid and oleiferous hyphae lacking.

Clamp connections

Absent.

NOTES

The description is based on two collections gathered by E. Horak one year before the species was officially described by R.F.R. McNabb (1973) as R. purpureotincta . Our description is highly similar to the original description, considering that the spore size given by McNabb (9-12 × 8.5-10.5 µm) includes the spore ornamentation. In addition, McNabb was probably not aware of the concept of ‘primordial hyphae’.

This endemic species of New Zealand seems to be widely distributed and not rare at all as many records are reported online (e.g. onhttps://scd.landcareresearch.co.nz). The online available field images, illustrations of microscopic features and SEM pictures of the spores for these collections (including for the type collection) clearly confirm our own observations on Horak’s specimens.

Russula purpureotincta is represented in our ITS phylogeny by nine sequences, including one newly produced sequence from the type specimen and one [GU222259 for PDD77740] that corresponds to a very pale collection initially identified as Russula cremeo-ochracea (and still deposited as such in GenBank). McNabb’s species resembles our R. incrustata Buyck , sp. nov. because of the faint greyish magenta, greyish purple to reddish grey tints present in the pileus, but it lacks the warmer orange-red tints of our New Caledonian species which, in addition, has a coloured stipe. As evident from online published pictures for R. purpureotincta , the stipe can frequently be obclavate and can vary considerably in length between different specimens.

Russula purpureotincta is very variable in overall colour, but typically discolours very rapidly leaving a pale sordid whitish-isabelline pileus with only faint greenish-pinkish hues remaining in the center and at the very margin of the pileus. Such discoloured specimens are more reminiscent of equally discoloured forms of several (but acrid!) species in the Russula core clade, rather than of other species of subsection Roseinae .

Microscopic differences between Russula purpureotincta and both above-mentioned New Caledonian species are very subtle. Spore ornamentation in McNabb’s species seems less reticulate, its cystidia on the gill edge more strongly thick-walled, and cystidial contents more abundant.

Figures

FIG. 15. — Russula purpureotincta R.F.R. McNabb (ZT 68-105): A-B, elements of the pileipellis near pileus margin: A, primordial hyphae with indication of contents in few cells; B, terminal cells of the other hyphal extremities. C-D, elements of the pileipellis in the pileus center: C, primordial hyphae without indication of contents; D, terminal cells of other hyphal extremities. Drawings B. Buyck. Scale bar: 10 µm.

FIG. 16. — Russula purpureotincta RFR. McNabb. Elements of the hymenium (all from ZT 68-105, except B from ZT 68-086). A-B, basidiospores; C, basidia; D, basidiola; E, pleurocystidia; F, cheilocystidia. Drawings B. Buyck. Scale bar: 10 µm.

FIG. 17. — Russula purpureotincta R.F.R. McNabb. Fresh basidiomata (ZT 68-105). Photo E. Horak. Scale bar: 2 cm.

FIG. 18. — Russula purpureotincta R.F.R. McNabb. Fresh basidiomata (ZT 68-068). Watercolour by E. Horak.