Basidiomata small to medium sized. Pileus 35–46 mm in diam., hemispherical when young, then plano-convex to applanate, depressed at centre when mature, rarely infundibuliform, viscid when wet, brownish tinged, intermixed with greyish-yellow fringe, Verona Brown (XXIX13′′k), Chocolate (XXVIII7′′m), to Cinnamon Brown (XV15′k) at centre, sometimes with a tinge of Argus Brown (III13m) or Brussels Brown (III15m), Pecan Brown (XXVIII13′′i) or Hazel (XIV11′′k) when old and dry; margin acute, slightly incurved first, straight when mature, slightly undulate, often cracked, tuberculate-striate 10–15 mm from the edge inwards, peeling 1/5–1/4 towards the centre, Ochraceous Tawny (XV15′i), Mikado Brown (XXIX13′′i) or Tawny Olive (XXIX17′′i) when young, often Avellaneous (XL17′′′b), Cinnamon (XXXI15′′) to Clay Colour (XXIX17′′) when mature. Lamellae adnate, rarely sub-free, 2–5 mm in height at mid-radius of pileus, fragile, rarely forked near the stipe, interveined, pale cream tinged, White (LIII) when young, Cream Colour (XVI19′f) in age, often stained yellowish to brownish with Buckthorn Brown (XV17′i) to Yellow Ochre (XV17′); edge even, narrowing towards the pileus margin, 9–16 per cm near the pileus margin; lamellulae rare. Stipe subcentral to central, 2.5–4.7 × 1–1.4 cm, cylindrical to subclavate, rarely tapered towards the base, annulus absent, first smooth, then often longitudinally rugulose in age, White (LIII), rarely stained with brownish tinge of Aniline Yellow (IV19i) to Honey Yellow (XXX19′′), first stuffed, hollow when mature. Context 2–4 mm thick at the centre of pileus, initially White (LIII), Light Ochraceous-Salmon (XV13′d) to Primuline Yellow (XVI19′) when mature, unchanging or slowly turning Ochraceous-Tawny (XV15′) to Buckthorn Brown (XV17′i) when injured or touched, brittle; taste mild, rarely slightly acrid when young; odour indistinct. Spore print cream-coloured (Romagnesi IIc–IId).

Figure 2. 

Basidiomata A Russula indocatillus B R. straminella C–D R. subpectinatoides E–F R. succinea. Bars: 10 mm.

Figure 3. 

SEM photo of basidiospores A Russula indocatillus B R. straminella C R. subpectinatoides D R. succinea.

Figure 4. 

Russula indocatillus, holotype A basidiospores B basidia C hymenial cystidia D suprapellis in pileus centre E suprapellis in pileus margin.

Figure 5. 

Russula indocatillus, holotype A hyphal extremities in pileipellis margin B hyphal extremities in pileus centre.

Basidiospores [200/8/4] (4.9–) 5.3–6.8 (–7.3) × (4.7–) 5.0–5.9 (–6.3) μm, Q = (1.01–) 1.05–1.28 (–1.33) (Q = 1.18 ± 0.08), 6.1 × 5.5 μm in average, subglobose to broad ellipsoid, ornamentation composed of conical to verrucous amyloid warts of very different sizes, mostly isolated, rarely linked as short ridges or with occasional line connections, not reticulate, warts 0.7–1 μm in height; suprahilar spot inamyloid and indistinct. Basidia 27–39 × 8–9 μm, hyaline in KOH, clavate to subclavate, four-spored, projecting 15–20 μm beyond the hymenium; sterigmata 3–6 μm, pointed, often straight, slightly tortuous towards the tip. Hymenial cystidia rare, less than 200/mm², 56–70 × 6–9 μm, fusiform to subclavate, rarely subcylindrical, thin-walled, projecting 20–40 μm beyond the hymenium, apex often mucronate, contents sparse, unevenly distributed, granular, greyish in SV. Pileipellis two layered, composed of suprapellis (80–150 μm thick) and subpellis (100–150 μm thick). Suprapellis an ixotrichoderm at pileus centre, composed of oblique to erect, septate, hyaline hyphae; acid-resistant encrustations absent, terminal cells cylindrical to subcylindrical, apex obtuse, rarely mucronate, mostly 40–70 μm in length; pileus margin a trichoderm composed of repent to tilted elements, terminal cells mostly 7–20 (–25) μm in length, ampullaceous, ellipsoid or cylindrical, obtuse to mucronate at apex, longer terminal cells similar to those in pileus centre also present; subapical cells contain islands of more or less inflated, 2–4 septate cells. Pileocystidia present in suprapellis and subpellis, abundant at pileus centre, dispersed at margin, one-celled, subulate, lageniform, fusiform, cylindrical, rarely appendiculate, 4–6 μm in width, many in suprapellis 15–25 μm in length, others up to 60 μm, even reaching a length of 100 μm in subpellis, apex mucronate, acicular to lanceolate in suprapellis, obtuse in subpellis, contents granulate, sparse, greyish in SV. Subpellis composed of repent to irregularly interlaced, inflated, septate hyphae 3–5 μm wide. Clamp connections absent in all tissues.

China, Guizhou Province, Weining Yi, Hui, and Miao Autonomous County, Caohai National Nature Reserve, 26°53'N, 104°12'E, alt. 2171 m, on the ground in coniferous forest, 9 September 2017, C.Y. Deng A (HGAS-MF 009903); ibid, alt. 1987 m, C.Y. Deng dcy2306 (HGAS-MF 009918); ibid, alt. 2053 m, C.Y. Deng dcy2303 (HGAS-MF 009911); ibid, alt. 2106 m, C.Y. Deng CH2017090971 (HGAS-MF 009917).

Single to scattered on yellow brown soil in coniferous forest dominated by Pinus armandii and P. yunnanensis at 1900–2200 m altitude.

China (Guizhou) and India (Uttarakhand).

The Chinese collections fit well with the original description of Ghosh et al. (2020), except for a few differences. The Indian specimens have longer basidia, 35–60 × 9–11 μm. The original description of R. indocatillus also noted that the type specimen was collected in a temperate mixed forest with Myrica, Quercus and Rhododendron. The coniferous tree species in this habitat were not mentioned. The Chinese collection is from a subalpine coniferous forest of subtropical region dominated by Pinus spp. with the main undergrowth species of Berberis cavaleriei, Corylus yunnanensis, Elaeagnus umbellata and Rosa sweginzowii (He et al. 2019).

Amongst the closely-related species in Clade H, R. amoenolens Romagn. and R. cerolens Shaffer have a strongly acrid taste, disagreeable sub-spermatic odour, basidiospore length up to 9 μm and longer hymenial cystidia up to 100 μm (Shaffer 1972; Romagnesi 1985; Sarnari 1998); R. catillus lacks lamellulae, has longer basidia 42–49 × 9.3–11.7 μm, shorter pileipellis terminal cells 41–72 × 3–7 μm and lacks pileocystidia (Lee et al. 2017); R. pseudocatillus has larger basidiospores 7–9.2 × 5.1–6.7 μm with higher ornamentation (up to 1.2 μm) which is never reticulate (Yuan et al. 2019).

Some members of R.sect. Ingratae, which were originally described from Himalayan Mountains and adjacent south-western China, may be confused with R. indocatillus in the field. Their main morphological differences are as follows: R. abbotensis has a crustose to areolate pileus with purplish-red to reddish-brown tinges, an ixotrichoderm pileipellis with pileocystidia 5 μm in width and an occurring in ectomycorrhizal association with Quercus spp. (Das and Sharma 2005); R. arunii can be distinguished by its fishy odour, amyloid suprahilar spot, 3–4 μm wide pileocystidia, mostly with a capitate apex and habitat in a tropical rain forest of Pterygota alata (Crous et al. 2017); R. ahmadii has larger basidiospores (5.6–) 6.1–9.2 (–9.4) × (5–) 5.1–6 (–6.5) μm with low (up to 0.3 μm high), partly reticulated ornamentation and cutis type of pileipellis (Jabeen et al. 2017); R. foetentoides can be distinguished from R. indocatillus by its smooth pileus margin, absence of lamellulae and its basidiospore ornamentation of 1.7–2 µm in height (Razaq et al. 2014); R. natarajanii differs in having larger basidiospores, 6.8–8.8 × 5.8–7.1 μm and longer hymenial cystidia, 60–90 × 6–10.5 μm (Das et al. 2006); R. pseudopectinatoides has larger basidiospores (6–) 6.5–9 (–9.5) × (5–) 5.1–6 (–6.5) μm with partly reticulate ornamentation, longer hymenial cystidia up to 90 μm and terminal cells of suprapellis hyphae often with obtuse to ventricose apex (Li et al. 2015b); R. succinea differs in larger basidiospores with incompletely reticulated ornamentations, longer basidia and pileocystidia up to 10 μm in width (Figs 10 and 11); R. tsokae can be distinguished from R. indocatillus by its larger basidiomata 8–13 cm in diam., yellowish-orange tinged stipe and larger basidiospores 6.8–8.8 × 5.8–7.1 μm with reticulated ornamentation up to 2 μm high (Das et al. 2010).

referring to the yellowish tinged pileus

China, Guizhou Province, Guiyang City, Yunyan District, Guizhou Botany Garden, 26°37'N, 106°43'E, alt. 1107 m, on the ground in coniferous forest, 8 July 2017, C.Y. Deng 2017–209 (HGAS-MF 009922, Holotype). GenBank accession: MN649195 (ITS).

This species is characterized by the yellow, brownish-yellow to brown pileus, tuberculate-striate margin, adnate lamellae tinged ochraceous when bruised, rare lamellulae, white stipe turning brownish-yellow when injured, mild to rarely acrid context, cream spore print, globose, subglobose to broad ellipsoid basidiospores (5.4–) 5.8–7.1 (–7.6) × (4.7–) 5.1–6.5 μm, 6.4 × 5.6 μm on average, with verrucous to conical, partly reticulate ornamentations 0.7–1 μm in height, subclavate to clavate basidia 33–40 × 9–11 μm, clavate to subclavate hymenial cystidia 56–70 × 8–10 μm, a suprapellis composed of two layers, a trichoepithelium at pileus centre and an ixotrichoderm towards the margin, pileocystidia abundant at pileus centre, but sparse in margin, a cutis type of subpellis and habitat on the ground in coniferous forests.

Figure 6. 

Russula straminella, holotype A basidiospores B basidia C hymenial cystidia D suprapellis and partial subpellis in pileus centre E suprapellis in pileus margin.

Figure 7. 

Russula straminella, holotype A hyphal ends in pileipellis margin B hyphal ends in pileus centre.

Basidiomata small to medium sized. Pileus 33–57 mm in diam., initially flat to hemispherical, then plano-convex to applanate, finally often concave at centre, gelatinised, yellowish to brownish-yellow tinged, intermixed with brownish fringe, Argus Brown (III13m), Warm Sepia (XXIX13′′m), to Verona Brown (XXIX13′′k) at centre, rarely with a paler tinge of Mikado Brown (XXIX13′′i), Rood’s Brown (XXVIII11′′k) to Cacao Brown (XXVIII9′′i); margin acute to subacute, enrolled when young, often undulate, sometimes cracked when mature, tuberculate-striate 8–15 mm from the edge inwards, peeling 1/5–1/4 towards the centre, first Aniline Yellow (IV19i), Sayal Brown (XXIX15′′) to Cinnamon Buff (XXIX15′′d), finally Mikado Brown (XXIX13′′i), Snuff Brown (XXIX15′′k) to Clay Colour (XXIX17′′). Lamellae adnate, fragile, occasionally forked near the stipe and pileus margin, interveined, first White (LIII), then of Cream Colour (XVI19′f) when mature, often having an ochraceous tinge of Olive Ochre (XXX21′′), Isabella Colour (XXX19′′i) to Honey Yellow (XXX19′′) when bruised, taste mild to slightly acrid; edge even, narrowing towards the pileus edge, 8–16 pieces per cm in the edge; lamellulae rare. Stipe central, 3.5–6.5 × 1–1.5 cm, cylindrical, slightly tapering towards the base, annulus absent, first smooth, slightly longitudinally rugulose when mature, White (LIII) when young, turning a pale brownish-yellow tinge of Kaiser Brown (XIV9′k), Aniline Yellow (IV19i) to Buckthorn Brown (XV17′i) after bruising, initially stuffed, fistulous to hollow when mature. Context White first, slowly turning a pale ochraceous tinged of Yellow Ochre (XV17′) to Ochraceous-Buff (XV15′b) when injured, 2–4 mm thick at the centre of pileus, compact; taste mild, rarely slightly acrid, with no distinct odour. Spore print cream coloured (Romagnesi IIc–IId).

Basidiospores [150/6/3] (5.4–) 5.8–7.1 (–7.6) × (4.7–) 5.1–6.5 μm, Q = (1.00–) 1.03–1.28 (–1.31) (Q = 1.15 ± 0.07), 6.4 × 5.6 μm in average, globose, subglobose to broadly ellipsoid, rarely ellipsoid, ornamentation amyloid, composed of verrucous to conical warts 0.7–1 μm in height, often linked by fine lines as short ridges, partly reticulate, rarely isolated; suprahilar area inamyloid, but distinct. Basidia 33–40 × 9–11 μm, hyaline, often yellowish in KOH, subclavate to clavate, sometimes cylindrical, mostly with four sterigmata 4–7 μm long. Hymenial cystidia rare, less than 500/mm², 56–70 × 8–10 μm, clavate to subclavate, rarely subfusiform, projecting 20–40 μm beyond hymenium, apex rounded, contents sparse, granular, evenly distributed, pale greyish in SV. Pileipellis two-layered, clearly distinguished from the subjacent sphaerocytes. Suprapellis 70–130 μm thick, acid-resistant encrustations absent, a trichoepithelium at pileus centre, partly an ixo-trichoepithelium, composed of erect to suberect hyphae, terminal cells cylindrical, 20–40 × 3–5 μm, obtuse at apex, partly ventricose, subapical cells sometimes inflated, rarely branched, 15–25 × 8–12 μm, an ixotrichoderm at pileus margin, composed of erect to ascending, rarely repent hyphae, terminal cells 30–55 × 3–5 μm, cylindrical, often thick-walled, tapered to mucronate at apex. Pileocystidia abundant, often fasciculate at pileus centre, narrowly lanceolate to bayonet-shaped, 30–60 × 5–8 μm, one-celled, contents granular, blackish-grey in SV. Pileocystidia sparse at the pileus margin, cylindrical, 4–8 μm in width, slightly tapered at apex, contents grey in SV. Subpellis composed of loosely interwoven, mostly repent, septate hyphae often inflated, 3–8 μm in width. Clamp connections absent in all tissues.

China, Guizhou Province, Guiyang City, Yunyan District, Guizhou Botany Garden, 26°37'N, 106°43'E, alt. 1074 m, on the ground in coniferous forest, 8 July 2017, C.Y. Deng dcy2305 (HGAS-MF 009920, paratype); ibid, alt. 1385 m, C.Y. Deng dcy2302 (HGAS-MF 009925, paratype).

Single to scattered on yellow brown soil in coniferous forest dominated by Pinus armandii and P. massoniana at 1100–1400 m altitude.

China (Guizhou).

This new species can be distinguished from members of R. sect. Ingratae described from China and the Himalayan region as follows: Russula gelatinosa, R. guangdongensis Z.S. Bi & T.H. Li, R. punctipes, R. senecis, R. subpunctipes and R. tsokae have basidiospore ornamentation composed of high wings (often above 2 μm), ranging over long distances or even encircling (Bi and Li 1986; Song et al. 2018, 2020). The Asian species of R.sect. Ingratae, R. ahmadii, R. natarajanii and R. pseudopectinatoides have basidiospore ornamentation lower than 0.7 μm (Das et al. 2006; Li et al. 2015b; Jabeen et al. 2017). For species that have similar basidiospore ornamentation, R. abbotensis has reddish-brown to purplish-red tinges on pileus surface, pruinose to scurfy stipe at base, larger basdiospores, 8–10 × 7.3–8.5 μm and hymenial cystidia with mucronate apices (Das and Sharma 2005); R. arunii has pileus turning light orange to greyish-orange when old, context having a fishy odour and narrow pileocystidia 3–4 μm in width (Crous et al. 2017); R. indocatillus has hymenial cystidia with mucronate, capitate, moniliform, rostrate or appendiculate apex with cylindrical or slightly inflated subapical cells (Ghosh et al. 2020); R. obscuricolor has a pale yellowish-white tinge in pileus margin, pungent and bitterish context, narrow pileocystidia 3–5 μm in width (Das et al. 2017); R. pseudocatillus has greyish-brown pileus centre, towards the margin very pale yellow, larger basidiospores, 7–9 μm in diam. and narrower pileocystidia (3–6 μm in width) unchanging in SV (Yuan et al. 2019); R. rufobasalis has reddish stipe base, mucronate or appendiculate apex of hymenial cystidia and thick-walled terminal cells (Song et al. 2018).

named for its morphological resemblance to R. pectinatoides Peck.

China, Jiangsu Province, Nanjing City, Qixia District, Nanjing Normal University, 32°06'N, 118°54'E, alt. 84 m, on the ground in coniferous forest, 28 August 2018, Q.B. Sun 2018001 (HBAU15030, Holotype). GenBank accession: MW1041163 (ITS).

This species is characterised by the greyish-brown to brownish-yellow pileus, striate margin, adnate to subadnate lamellae rarely staining reddish-brown when bruised, infrequent lamellulae, context slowly turning pale ochre after injury and slightly to moderately acrid taste, cream spore print, subglobose to broadly ellipsoid basidiospores (5.3–) 5.6–6.3–7 (–7.3) × (4.1–) 4.6–5.2–6 (–6.3) μm, ornamentation 0.3–0.5 μm in height, composed of long ridges forming an incomplete to complete reticulum, fusiform to subclavate, basidia 27–50 × 8–12 μm, fusiform to subclavate hymenial cystidia 56–73 × 6–12 μm, pileipellis with one-celled, slender, mucronate, conical, needle-shaped to cylindrical pileocystidia, 5–7 μm in width; and habitat in coniferous forest.

Figure 8. 

Russula subpectinatoides, holotype A basidiospores B basidia C hymenial cystidia D suprapellis in pileus centre E suprapellis in pileus margin.

Figure 9. 

Russula subpectinatoides, holotype A hyphal extremities in pileipellis margin B hyphal extremities in pileus centre.

Basidiomata small to medium-sized. Pileus 18–95 mm in diam., initially hemispherical, concave at centre, turning applanate with age, often depressed at stipe, slightly viscous when young or humid, greyish-brown to brownish-yellow tinged, intermixed with dark brown fringe, Buffy Citrine (XVI19′k) to Light Brownish Olive (XXX19′′k) at centre, Citrine-Drab (XL19′′′i), Drab (XLVI17′′′′) to Benzo Brown (XLVI13′′′′i) when mature, often turning Buffy Olive (XXX21′′k) to Saccardo’s Olive (XVI19′m) when old and dry; margin acute to subacute, involute when young, straight with maturity, sometimes dehiscent, undulate to curled-up when old, striate 1/4–1/3 towards the centre, not or rarely weakly tuberculate, peeling 1/5–1/3 towards the centre, rarely flaking in small patches, with an ochre tinge of Old Gold (XVI19′i), Olive Ochre (XXX21′′) to Tawny-Olive (XXIX17′′i). Lamellae adnate to subadnate, 3–6 mm in height at the midpoint, sometimes forked near the stipe and the pileus edge, interveined, white to pale cream, White (LIII) when young, Light Buff (XV17′f) to Cream Colour (XVI19′f) with age, rarely stained reddish-brown tinge of Buckthorn Brown (XV17′i) when bruised, taste slightly to moderately acrid; edge even, constricted towards the margin, 9–19 pieces per cm at the edge; lamellulae infrequent. Stipe central to subcentral, 2.4–9.3 × 1.3–2.7 cm, slightly narrowing towards the base and apex, smooth at first, longitudinally slightly rugulose when mature, White (LIII) first, sometimes faintly stained with Honey Yellow (XXX19′′) to Olive Ochre (XXX21′′) when bruised, stuffed first, fistulous to hollow when old. Context 2–5 mm thick above the stipe, initially White (LIII), unchanging or slowly turning pale ochre tinge of Cinnamon Buff (XXIX15′′d) when bruised, pale greyish-yellow tinge of Cartridge Buff (XXX19′′f) at base when old, taste slightly to moderately acrid, with no distinct odour. Spore print cream coloured (Romagnesi IIc–IId).

Basidiospores [250/10/5] (5.3–) 5.6–7 (–7.3) × (4.1–) 4.6–6 (–6.3) μm, Q = (1.02–) 1.05–1.31 (–1.37) (Q = 1.19 ± 0.09), 6.3 × 5.2 μm in average, mostly subglobose to broadly ellipsoid, rarely globose and ellipsoid, ornamentation amyloid, composed of long ridges forming an incomplete to complete reticulum, rarely intermixed with an isolated conical to verrucous warts and short crests, 0.3–0.5 μm in height; suprahilar spot inamyloid and indistinct. Basidia 27–50 × 8–12 μm, hyaline in KOH, subcylindrical to subclavate, rarely clavate or subfusiform, inflated towards the upper end or mid-piece, 4-spored, projecting 15–30 μm beyond hymenium; sterigmata 3–6 μm, slightly tortuous, sometimes straight. Hymenial cystidia sparsely distributed, fewer than 200/mm², 56–73 × 6–12 μm, fusiform to subclavate, projecting 20–40 μm beyond the hymenium, contents granular, sparsely distributed, slightly greyish in SV; apex subacute, rarely obtuse; lamellar edge sterile. Pileipellis two layered, composed of suprapellis (80–140 μm thick) and subpellis (100–150 μm thick). Suprapellis an ixotrichoderm, composed of gelatinised, ascending to vertical, septate hyphae, acid-resistant encrustations absent, terminal cells mostly lanceolate to bayonet-shaped at pileus centre, mostly tapered at apex, rarely cylindrical, 20–30 × 4–7 μm, subapical cells sometimes inflated, barrel-shaped, ellipsoid or almost subglobose to globose; when compared with suprapellis at pileus centre, its margin is also an ixotrichoderm, but contains more repent elements, 3–5 μm in width, inflated hyphal cells not observed, lateral short ramifications frequent; pileocystidia long, cylindrical, non-septate, 3–5 μm in width, apex mucronate, contents granulate, sparse, pale grey in SV. Subpellis a composed of cylindrical, sometimes inflated, septate, loosely intricate, gelatinous, hyaline hyphae 3–6 μm in width. Clamp connections absent in all parts.

China, Jiangsu Province, Nanjing City, Qixia District, Nanjing Normal University, 32°06'N, 118°54'E, alt. 84 m, on the ground in coniferous forest, 28 August 2018, Q.B. Sun 2018002 (HBAU15031, paratype); ibid, 2018003 (HBAU15032, paratype); ibid, 2018004 (HBAU15033, paratype).

Single to scattered on yellow brown soil in coniferous forest of subtropical monsoon climate zone dominated by Cedrus deodara, Pinus parviflora and P. thunbergii.

China (Jiangsu).

This new species is similar to R. pseudopectinatoides in its brownish-yellow pileus, slightly acrid taste, cream spore print, spores with low, subreticulate ornamentation and gelatinous pileipellis. It is notable that basidiomata of R. subpectinatoides were collected from a forest of introduced coniferous tree species. Cedrus deodara is native in the western Himalayas, while Pinus parviflora and P. thunbergii are naturally distributed in the Japanese archipelago and Korean peninsula. Therefore, this new taxon may also occur in these introduced areas with its accompanying trees.

The Asian species of sect. Ingratae already recognizable by their long slender stipe, such as R. gelatinosa, R. guangdongensis, R. punctipes, R. senecis, R. subpunctipes and R. tsokae and cannot be confused with our new species, even more so because they have basidiospores composed of long wings, 2 μm high or more (Song et al. 2018, 2020). A similarly-winged spore ornamentation also differentiates species of the R. grata lineage which, moreover, usually have a distinct bitter almond smell. The more golden yellow pileus of species in the R. foetens or R. subfoetens lineages also avoids confusion with our new species and because many of these are distinctly very acrid. The strong yellowish stipe base that turns immediately red with KOH easily allows one to distinguish the few species of the R. insignis lineage. In the R. granulata lineage, the Asian species R. rufobasalis has reddish tinged stipe base, pleurocystidia with mucronate or appendiculate apices and longer terminal cells, up to 60 μm (Song et al. 2018). Finally, the typically very acrid taste allows us to eliminate most species of the R. amoenolens lineage, notwithstanding their sometimes quite similar colouration. The same very acrid taste also differentiates R. obscuricolor, which was described from the Indian Himalayas (Das et al. 2017) and showed close affinity to some Southern Hemisphere Ingratae in our phylogeny.

After application of these criteria, we are principally left with the phylogenetically closer species of the R. praetervisa lineage as potential sources of confusion, most of which are mild to merely slightly acrid. From Asia, this concerns essentially R. pseudopectinatoides, a species that can be distinguished by its larger basidiospores (6–) 6.5–9 (–9.5) × 5–7.5 (–8) μm, hymenial cystidia sometimes with moniliform or capitate appendages and terminal cells of pileipellis with obtuse to ventricose apices (Li et al. 2015b); R. ahmadii differs in small basidiomata with pileus 1–4.5 cm in diam. and pileipellis a cutis with bifurcated terminal cells (Jabeen et al. 2017). The European species R. recondita Melera & Ostellari has a fruity-acidic, but overall unpleasant context smell, larger basidiospores 7–8.5 × 5.5–7 μm, with ornamentation composed of mostly isolated obtuse conical warts up to 1 μm high (Melera et al. 2017). From North America, R. amerorecondita Avis & Barajas has a strongly tuberculate-striate pileus margin, white to pale cream spore print, larger basidiospores (6.5–) 7.1–7.6–8.1 (–9.5) × (5–) 5.6–6.3–6.9 (–8) μm with more isolated ornamentation and a habitat in hardwood forest dominated by Quercus; R. garyensis Avis & Barajas has context with unpleasant, bleachy, fishy to parmesan smell, higher basidiospore ornamentation (0.6–) 0.8–1 (–1.4) μm, longer hymenial cystidia (62–) 71.5–81.4–91 (–103) × 7–8.1–9 (–10) μm and apex sometimes with two, long, usually narrow appendages (Adamčík et al. 2019).

referring to the pale brownish tinged pileus.

China, Guizhou Province, Weining Yi, Hui, and Miao Autonomous County, Caohai National Nature Reserve, 26°53'N, 104°12'E, alt. 2183 m, on the ground in coniferous forest, 15 July 2017, C.Y. Deng CH2017071509 (HGAS-MF 009904, Holotype). GenBank accession: MN649188 (ITS).

This species is characterised by the yellowish-brown to pale brown pileus, with tuberculate-striate margin, adnate and pale cream-coloured lamellae, subclavate to subcylindrical stipe turning cream to pale ochre when bruised, white context unchanging after injury, slightly acrid to mild taste, pale cream spore print, globose, subglobose to broadly ellipsoid basidiospores (5.8–) 6.1–7.8 (–8.3) × (4.9–) 5.2–6.8 (–7.3) μm, 7.0 × 6.0 μm on average, ornamentation 0.8–1.2 μm in height, forming incomplete reticulum, rarely intermixed with isolated warts, clavate to subcylindrical basidia, 44–66 × 10–12 μm, fusiform hymenial cystidia 71–88 × 9–15 μm, two-layered pileipellis, ixotrichodermal suprapellis in pileus centre, a trichoderm at the margin, subpellis a cutis and habitat in coniferous forests.

Figure 10. 

Russula succinea, holotype A basidiospores B basidia C hymenial cystidia D suprapellis partial subpellis in pileus centre E suprapellis in pileus margin.

Figure 11. 

Russula succinea, holotype A hyphal ends in pileipellis margin B hyphal ends in pileus centre.

Basidiomata small to medium sized. Pileus 32–54 mm in diam., initially hemispherical, then plano-convex, flat when mature, often slightly depressed at centre, strongly viscid when wet, yellowish-brown tinged, pale brownish tinged, often intermixed with greyish-yellow fringe, Hazal (XIV11′k), Russet (XV13′k), Cinnamon Brown (XV15′k) to Tawny (XV15′) at centre, rarely with Liver Brown (XIV17′m), Pecan Brown (XXVIII13′′i) or Rood’s Brown (XXVIII11′′k) when old and dry; margin subacute to acute, straight, rarely split or inward-turned, tuberculate-striate 14–25 mm from the edge inwards, peeling 1/3–1/2 towards the centre, pale yellowish tinged, first Deep Colonial Buff (XXX21′′b), Honey Yellow (XXX19′′) to Light Ochraceous Salmon (XV13′d), then Light Cadmium (IV19), Maize Yellow (III19f) when mature. Lamellae adnate, 3–6 mm in height at the halfway point of pileus radius, brittle, often forked near the stipe and pileus edge, interveined, pale cream-coloured, first White (LIII), Cream Colour (XVI19′f) when mature, sometimes stained with Martius Yellow (III23f) to Baryta Yellow (IV21f); edge entire, narrowing towards the pileus margin, 13–22 pieces per cm in the edge; lamellulae absent. Stipe slightly subcentral, rarely central, 4.2–8.3 × 1.5–2.2 cm, subclavate to subcylindrical, often narrowing towards the base, rarely slightly curved, smooth when young, rugulose longitudinally in age, dry, Cream Colour (XVI19′f), staining Sudan Brown (III15k) to Orange-Citrine (IV19k) when bruised, Tawny Olive (XXIX17′′i), Sayal Brown (XXIX15′′) to Isabella Colour (XXX19′′i) at base, initially solid, turning hollow in age. Context White (LIII), unchanging when bruised or touched, 3–5 mm thick at the centre of pileus, fragile, taste first slightly acrid, mild when mature, odour indistinct. Spore print pale cream (Romagnesi IIc–IId).

Basidiospores [350/14/7] (5.8–) 6.1–7.8 (–8.3) × (4.9–) 5.2–6.8 (–7.3) μm, Q = (1.00–) 1.03–1.30 (–1.33) (Q = 1.17 ± 0.08), 7.0 × 6.0 μm on average, globose, subglobose to broadly ellipsoid, rarely ellipsoid, composed of verrucous to subcylindrical amyloid warts 0.8–1.2 μm in height, often linked as short to long crests and ridges, forming an incomplete reticulum, rarely intermixed with isolated warts; suprahilar spot distinct, but not amyloid. Basidia 44–66 × 10–12 μm, mostly 4-spored, clavate to subcylindrical; sterigmata 4–6 μm in length, straight to tortuous. Hymenial cystidia moderately numerous, ca. 700–1300/mm², 71–88 × 9–15 μm, fusiform, sometimes cylindrical, thin-walled, apex obtuse, rarely mucronate, projecting 20–40 μm beyond the hymenium, contents granular to crystalline, partly dense, blackish-grey in SV. Pileipellis two-layered, distinctly delimited from the underlying context. The upper suprapellis (70–130 μm thick) in pileus centre an ixotrichoderm, composed of ascending to erect hyphae 4–7 μm in width, septate, cylindrical, often slightly inflated, acid-resistant encrustations absent, terminal cells sometimes narrowing towards the apex, subapical cells cylindrical, not branched; suprapellis a trichoderm in pileus margin, composed of repent, slender, cylindrical, hyaline hyphae 3–5 μm in width, acid-resistant encrustations absent. Pileocystidia abundant, long, cylindrical, often septate, 4–10 μm in width, apex obtuse, contents granulate, dense, blackish-grey in SV. The lower layer subpellis (50–90 μm thick) composed of loosely interwoven, mostly repent, cylindrical, septate hyaline hyphae often inflated, 2–7 μm in width. Clamp connections not observed in all parts.

China, Guizhou Province, Weining Yi, Hui and Miao Autonomous County, Caohai National Nature Reserve, 26°53'N, 104°12'E, alt. 2215 m, on the ground in coniferous forest, 16 July 2017, C.Y. Deng CH2017071602 (HGAS-MF 009915, paratype); ibid, alt. 2136 m, 15 July 2017, C.Y. Deng dcy2307 (HGAS-MF 009909, paratype); ibid, alt. 2005 m, C.Y. Deng dcy2309 (HGAS-MF 009906, paratype); alt. 2057 m, C.Y. Deng dcy2308 (HGAS-MF 009902, paratype); alt. 2103 m, C.Y. Deng dcy2304 (HGAS-MF 009914, paratype); Jiangxi Province, Jiujiang City, Lushan City, Lushan Mountains, alt. 1257 m, on the ground in coniferous forest, 19 October 2016, J.B. Zhang (HFJAU 0301).

Single to scattered on yellow brown soil in coniferous forest dominated by Pinus armandii, P. massoniana and P. yunnanensis at 1200–2200 m altitude.

China (Guizhou and Jiangxi).

This new species is reminiscent of R. foetentula, R. obscuricolor and R. rufobasalis because of the reddish-brown or burnt sienna colour at the stipe base (Peck 1907; Song et al. 2018). The following characters are helpful for differentiating these two species from R. succinea: R. foetentula has lower basidiospore ornamentations 0.5–0.9 μm connected by occasional to rare line connections, hymenial cystidia with mucronate-appendiculate apices 2–7 μm long, pileocystidium apex often constricted to 1–2.5 μm in width; North American distribution (Peck 1907; Adamčík et al. 2013); R. obscuricolor has darker brown to chocolate brown tinges at pileus centre, bitter to pungent taste of context and shorter hymenial cystidia (pleurocystidia 30–65 × 6–9 μm, cheilocystidia 23–33 × 5–7 μm) (Das et al. 2017); R. rufobasalis has bright reddish tinge at stipe base, basidiospore ornamentations 0.3–0.8 μm in height and frequently thick-walled, narrower terminal cells 2–5 μm in width (Song et al. 2018).

For those Asian sect. Ingratae members that have similar pileus tinges, R. ahmadii can be distinguished from R. succinea by lower basidiospore ornamentations up to 0.3 μm, shorter basidia (29–) 29.7–38.9 (–40.1) × (9.2–) 9.4–11.3 (–11.8) μm and pileipellis a cutis (Jabeen et al. 2017); R. arunii differs from the new species in the orange tinge intermixed on pileus surfaces, white spore print, narrow pileocystidia 3–4 μm in width and a habit of broad-leaved Pterygota alata forest (Crous et al. 2017); R. catillus differs in that basidiospore ornamentation is composed of mostly isolated, verrucous to conical warts, absence of pileocystidia in pileipellis and a habitat of oak hardwood forest (Lee et al. 2017); R. indocatillus can be differentiated from the new species for white spore print, shorter basidia 34–40 × 9–11 μm and capitate hymenial cystidium apex (Ghosh et al. 2020); R. natarajanii differs in having light to medium brown spots at the pileus periphery, shorter basidia 28–35 × 7.5–9 μm and a habitat of Quercus forest (Das et al. 2006); R. pseudocatillus differs in the presence of lamellula, basidiospores ornamented with isolated warts never forming a reticulum and a habitat of broad-leaved evergreen forest (Yuan et al. 2019); R. pseudopectinatoides can be distinguished from the new species in having hymenial cystidia with moniliform or capitate apex, larger basidiospores up to 9 μm in diam. and absence of pileocystidia (Li et al. 2015b); R. straminella differs in its shorter basidia and hymenial cystidia, often thick-walled terminal cells in pileipellis of pileus margin (Figs 6 and 7); R. gelatinosa, R. punctipes, R. seneicis, R. subpunctipes and R. tsokae differ from R. succinea in their larger basidiospores (9 μm in diam.) with high ornamentation up to 2 μm in height (Khatua et al. 2015; Lee et al. 2017; Song et al. 2018; 2020).