Russula megapseudocystidiata X.Y. Sang & L. Fan, 2016

Sang, Xiaoyu, Li, Xuedong, Wang, Yanwei & Fan, Li, 2016, Four new sequestrate species of Russulaceae found in China, Phytotaxa 289 (1), pp. 101-117 : 112

Russula megapseudocystidiata X.Y. Sang & L. Fan , sp. nov. ( Fig. 6 , Fig. 7D )

Mycobank: MB819371

Type:— CHINA. Sichuan: Panzhihua City, in soil under mixed woodlands dominated by P. yunnanensis , 23 Nov 2014, CJZ 1534-1, FAN 454 ( BJTC!), collected by J. Z. Cao (Holotype: BJTC FAN 454).

Basidiomata 20–24 × 18–20 mm, subglobose, plane to concave at apex and depressed at base. Peridial surface creamy white, yellowish-brown after drying, glabrous, rugulose and deeply grooved. Gleba ivory to grey white, margin pale yellow, loculate, locules irregularly dense. Stipe absent. Columella absent. Latex absent. Smell unremarkable.

Basidiospores globose to subglobose, 10–15 × 9–13 μm (x = 12.2 ± 1.7 × 11.7 ± 1.3, n = 30) excluding ornamentation, Q = 1.00–1.18, colorless to yellowish-brown, slightly thick-walled, completely dissociated after mature, ornamentation amyloid, composed of isolated spines 1–3 μm long, irregularly distributed, usually curved and coalescing the apex of 2 or 3 adjacent spines. Hilar appendix 2–3 μm long, central, cylindrical, straight. Basidia 23–46 × 6–15 μm, clavate to broadly clavate, broadly cylindrical, mostly 2-spored, the sterigmata up to 2–9 μm long. Pseudocystidia 40–90 × 5–12 μm, subclavate to clavate with rounded apices, projecting beyond basidia abundantly arising in trama. Cystidia 30–50 × 5–15 μm, fusoid or ventricose, apex obtuse, hyaline. Hymenophoral trama 40–100 μm wide, composed of interwoven, hyaline hyphae 2–3 μm diam., laticiferous hyphae 2.5–4 μm, sphaerocytes absent; subhymenium 16–40 μm wide, composed of pseudoparenchyma with 2–3 tiers of isodiametric cells 7.5–20 × 5–13 μm. Peridiopellis two-layered: a thin suprapellis composed of repent to erect, hyaline hyphae 10–55 × 2–8 μm; subpellis 45–90 μm thick, composed of irregular, agglutinated pseudoparenchyma with 4–6 tiers of cells 7–25 × 5–10 μm. Peridial context 42–75 μm wide, of loosely interwoven, hyaline hyphae 2–5 μm diam. and abundant laticiferous hyphae with refractive granular content, 3–6 μm diam., sphaerocytes absent.

Diagnosis:— Basidiomata 20–24 × 18–20 mm, subglobose. Peridial surface creamy white. Gleba white to ivory, loculate. Columella absent. Basidiaspores globose to subglobose, with isolated spines, usually curved and coalescing the apex of 2 or 3 adjacent spines. Basidia mostly 2-spored. Pseudocystidia present. Cystidia present.

Etymology: —Latin, megapseudocystidiata = large pseudocystidium, in reference to the large, clavate pseudocystidium in the hymenium.

Habit, habitat and distribution: —hypogeous, gregarious, in soil under mixed woodlands dominated by P. yunnanensis in Sichuan Province, China.

Commentary: — Russula megapseudocystidiata is characterized by the combination of long pseudocystidia, two-spored basidia, and basidiospores that are ornamented with isolated, curved spines and coalescing at the apex. Cystangium bisporum T. Lebel ( Lebel 2003: 373) and C. gamundiae Nouhra & Trierv. -Per. (Trierv.-Per. et al. 2015: 95) resemble the present species in morphology. Cystangium bisporum differs by its peridial context having abundant sphaerocytes and lacking laticiferous hyphae. Furthermore, the peridial surface of C. bisporum is smooth ( Lebel 2003), whereas it is rugulose and deeply grooved in R. megapseudocystidiata . Cystangium gamundiae is differentiated from R. megapseudocystidiata by its basidiomata that usually have the pink to vinaceous hues and columella, and basidiospores with robust, isolated, crowded spines (Trierv.-Per. et al. 2015).

Figures

FIGURE 6. Russula megapseudocystidiata (BJTC FAN454, holotype). A. Basidia. B. Pseudocystidia. C. Hymenophoral cystidia. D. Basidiospores. E. Peridiopellis and peridial context. F. Hymenophoral trama and hymenium. Scale bar = 10 μm.

FIGURE 7. Scanning electron micrograph (SEM) of basidiospores. A. Lactarius spinosporus (holotype). B. Russula absphaerocellaris (holotype). C. Russula brevipileocystidiata (holotype). D. Russula megapseudocystidiata (holotype). Scale bar = 5 μm.