Volvariella pusilla (Pers.) Singer, Lilloa

Caballero, Fernando, Justo, Alfredo, Parra, Luis A., Angelini, Claudio, Consiglio, Giovanni, Dovana, Francesco, Ferisin, Giuliano, Kaygusuz, Oğuzhan, Knudsen, Henning, Llimona, Xavier, Muñoz, Guillermo, Daniëls, Pablo P., Pérez-De-Gregorio, Miquel À., Ševčíková, Hana, Valverde, Andrés & Vizzini, Alfredo, 2025, Taxonomic and phylogenetic overview of the genus Volvariella (Volvariellaceae), with a focus on European species, Phytotaxa 680 (1), pp. 1-85 : 36-39

8. Volvariella pusilla (Pers.) Singer, Lilloa 22: 401. 1951 [“1949”]. ( Fig. 16 )

≡ Amanita pusilla Pers., Observationes Mycologicae 2: 36. 1800 [“1799”] [basionym]

≡ Agaricus pusillus (Pers.) DC. , in Lamarck & De Candolle, Flore Française (Ed. 3) 2: 211. 1805, nom sanct. (Fr., Syst. Mycol. 1: 279. 1821)

≡ Volvaria pusilla (Pers.) Quél., Flore Mycologique de la France et des Pays Limitrophes: 189. 1888

≡ Volvariopsis pusilla (Pers.) Murrill , North American Flora 10(2): 141. 1917

≡ Agaricus parvulus Weinm. , Hymeno- et Gastero-Mycetes Hucusque in Imperio Rossico Observatos: 238. 1836 (nom. illeg., Art. 52.1; type of Agaricus pusillus (Pers.) DC. , nom. sanct. Fr. not excluded)

≡ Volvaria parvula P. Kumm., Der Führer in die Pilzkunde: 99. 1871 (nom. illeg., Art. 52.2. Type of Agaricus pusillus (Pers.) DC. , nom. sanct. Fr. not excluded)

≡ Volvariella parvula Speg., Boletín de la Academia Nacional de Ciencias en Córdoba 28: 309. 1926 (nom. illeg., Art. 52.2. Type of Agaricus pusillus (Pers.) DC. , nom. sanct. Fr. not excluded)

Typification status:— Lectotype, designated here: [icon] Amanita pusilla in Pers., Observationes mycologicae 2: Tab. IV, Fig. 4 . 1800. MycoBank type: MBT 10023149.

Description:— Pileus 10–35(–50) mm diam., convex to conico-convex when young, expanding to plano-convex; surface finely fibrillose or silky-fibrillose or covered with fibrils grouped into small squamules, becoming smooth in mature specimens, white, sometimes with ochre yellow tinges at centre, not hygrophanous; margin slightly striate, irregular and exceeding the lamellae. Lamellae crowded, free, broadly ventricose, white when young, becoming salmon pink or pinkish brown with age; edge white and flocculose, or concolorous. Stipe 26–45 × 4–7 mm, cylindrical, slightly widening towards the base, straight; surface white, finely pubescent. Volva membranaceous, saccate, white or light ivory, with 2–3 lobes; rhizomorphs not observed. Context white, thin, with indistinct smell.

Basidiospores (n=132, c=4) 5.0–7.5(–8.0) × (3.75–)4.0–5.5 μm, avl × avw = 6.2 × 4.6 μm, Q = 1.22–1.58, avQ = 1.37, broadly ellipsoid to ellipsoid, thick-walled, with barely distinct hilar appendage. Basidia (20–)22–37 × 8– 12 μm, tetrasterigmate, clavate or subclavate. Lamella edge heterogeneous. Cheilocystidia common, 18–79 × 8–30 μm, lageniform with elongated neck, narrowly to broadly fusiform, less frequently vesiculose, thin-walled, hyaline. Pleurocystidia scarce, 37–70 × 10–32 μm, scattered, mostly broadly fusiform to fusiform, thin-walled, rarely thick-walled, hyaline. Pileipellis a cutis or an intermediate cutis-trichoderm, with hyaline, mostly cylindrical to narrowly clavate thin-walled terminal elements, 15–50 μm wide, often constricted at the septa. Stipitipellis a cutis, or a cutis-trichoderm in the upper part of the stipe, with cylindrical hyphae, 8–31 μm wide. Volva composed of interwoven, cylindrical hyphae, 3–21 μm wide, with few septa. Clamp connections absent in all parts examined.

Habit, habitat, and phenology:—Solitary or gregarious. Terrestrial, often collected in gardens in urban areas, also collected in lawns and forest areas. Recorded under Morus alba , Pinus halepensis , Pinus sp. and Populus alba . August–November.

Distribution:—Known with certainty from Europe.

Additional collections examined:— CZECH REPUBLIC. Moravia: Ostrov u Macochy, NR Balcarova skála - Vintoky, near Balcarka cave, in the lawn by the bench, 15 August 2019, P. Ševčík, BRNM817662. SPAIN. Balearic Islands: Mallorca, Camí des Correus, Esporles, among mosses on a slope, 31 October 1999, J.C. Salom, JCS295B; Barcelona: Sant Fost de Campsentelles, among the grass of a garden area, 8 September 2019, F. Caballero, SFC 190908; ibid., among the grass of a garden area, 11 September 2019, F. Caballero, SFC 190911; ibid., 15 September 2019, F. Caballero, SFC 190915; ibid., 30 September 2019, F. Caballero, SFC 190930; ibid., 2 October 2019, F. Caballero, SFC 191002-1; ibid., 25 August 2021, F. Caballero, SFC 210825; ibid., 4 September 2021, F. Caballero, SFC 210904; ibid., 14 September 2021, F. Caballero, SFC 210914; ibid., 16 September 2021, F. Caballero, SFC 210916; ibid., 24 September 2021, F. Caballero, SFC 210924; Bizkaia: path to Baraizpe wetland, Gautéguiz de Arteaga, elev. 74 m, on roadside verge among grass, 22 October 2023, L.A. Parra, LAP 192; Zaragoza: Parque Grande, garden area, under Pinus halepensis , 24 September 2010, G. Muñoz, GM1933.

Nomenclatural comments:—In order to establish whether V. pusilla is the correct name for the taxonomical concept adopted here it must be determined if Agaricus pusillus is a replacement name for Agaricus volvaceus (unranked) minor or the name of a new species because the type of A. pusillus would be different depending on the conclusion.

Both Persoon (1800) and Fries (1821) cited Agaricus volvaceus (unranked) minor Bulliard (1788) as being the same taxon as their Amanita pusilla and Agaricus pusillus respectively. Both authors incorrectly cite the plate of A. volvaceus (unranked) minor as “Table 530”, but this taxon is represented in Bulliard’s work in Table 330. Bulliard (1788) depicts A. volvaceus (unranked) minor as a small species with a grey, radially fibrillose pileus. Therefore, we consider that Bulliard’s taxon is not the same taxon as that described by Persoon and Fries with a white (“ albido ”) pileus. The taxonomical circumscription of these two latter authors has been unanimously adopted by subsequent authors from Quélet (1888) until today, and is accepted here, applying the name V. pusilla to a small species with an exclusively white pileus.

As Agaricus pusillus was not explicitly proposed as a substitute for an earlier name and Art. 6.12 does not apply, it can be treated as a replacement name or the name of a new taxon (Art. 6.13) because the potential synonym A. volvaceus (unranked) minor was cited and the requirements for valid publication of the name of a new taxon were independently met. In fact, Persoon (1800) explicitly stated that he saw it in autumn (“ autumno vidi ”), and he included a description and an illustration based on his own material. So, in agreement with Art. 6.13, we consider Amanita pusilla the name of a new species based on the predominant usage of the current V. pusilla as a different taxon from A. volvaceus (unranked) minor and in consequence we designate the appropriate type for each name as pointed out in Art. 6.13.

The modern correspondence of A. volvaceus (unranked) minor cannot be established with certainty, and since it was described at an undefined infraspecific rank, it has no nomenclatural priority over other names or defined infraspecific ranks of Volvariella assigned to small, grey species.

A. volvaceus ( unranked) minor Bull.: Lectotype, designated here: [icon] Agaricus volvaceus minor in Bull., Herbier de la France 7: Tab. 330, second figure on the right. 1788. MycoBank type: MBT 10023150.

On the other hand, we must elucidate whether Agaricus parvulus Weinm. is an illegitimate name and if it has to be considered a replacement name for Agaricus pusillus (Pers.) DC. or the name of a new species. Like Orton (1986), we believe that Weinmann (1836) was aware that Agaricus pusillus (Pers.) DC. (1805) was a later homonym of A. pusillus Schaeff. (1774) and he coined a new name for the former. This is obvious when one examines Weinmann’s work (1836) because he knew very well and mentioned numerous times Schaeffer’s work ( Schaeffer 1774) and in the protologue he included references to “ Agaricus pusillus Fr., Syst. Mycol 1. p. 279” and “ Amanita pusilla Pers. Syn. Fung. p. 249”. Even if these were not the original works in which both names were published for the first time and, therefore, the references could be interpreted as “in the sense of” these authors (see Art. 52.3; Note 3) we think that it is not the case because Weinmann (1836) described Agaricus parvulus with a white pileus with sooty greyish umbo (“ pileo membranaceo, planiusculo, sicco, albido, umbone fuligineo-cinereo ”) but in the works by Persoon and Fries referenced by Weinmann the pileus is described as white (“ albido ”). Furthermore, Weinmann also included references to Bulliard’s plate of “ Agaricus volvaceus minor ” (1788) showing a completely dark grey pileus and De Candolle (in Lamarck & De Candolle 1805) describing a whitish pileus, with small blackish and radial stripes (“ blanchâtre, avec de petites raies noirâtres et rayonnantes ”).

In Weinmann’s time the names published by Fries did not have special protected status and therefore his nomenclatural procedure of creating the replacement name Agaricus parvulus for Agaricus pusillus (Pers.) DC. was correct. However, the nomenclature rules are retroactive and currently the names published by Fries in Systema Mycologicum (1821–1832) and Elenchus fungorum (1828) are sanctioned and they are legitimate even if when they were published, they were illegitimate, as is the case for Agaricus pusillus (Pers.) DC. nom. sanct. Fr. Therefore, Weinmann’s name is now illegitimate because he should have adopted the name Agaricus pusillus (Pers.) DC. (Art. 52.1) which, being sanctioned, is legitimate (see Art. F.3.4, Ex. 3 last sentence).

In summary, Agaricus parvulus Weinm. is an illegitimate homotypic synonym of A. pusillus (Pers.) DC. So , in the present work, all specimens matching the original description of Weinmann (synonyms excluded) will be described as a new species under the name V. neoparvula .

Observations:—The above description is based exclusively on the collections examined here considered to represent V. pusilla .

Volvariella pusilla is characterized by the small, pure white basidiomes which only sometimes develop some ochre yellow tones in older specimens. It fruits often in gardens and urban parks, but it has also been recorded from forest ecosystems.

The concept of V. pusilla accepted here fits well with the original description of Amanita pusilla ( Persoon 1800) : a small, white species fruiting in gardens. The same concept was maintained by Fries (1821) for Agaricus pusillus (based on Amanita pusilla ). The phenology is recorded as “ autumn ” by Persoon and “ August ” by Fries, which also fits the phenology of the collections examined here.

The pure white colours of the basidiomes are generally a good diagnostic character of V. pusilla , although confusion is possible with other small white species or with white variants of normally pigmented species. Volvariella latispora differs in the translucently striate pileus margin and the larger basidiospores (7.7 × 5.2 µm on average). Volvariella globifera has slightly smaller basidiospores (5.8 × 3.9 µm on average). Volvariella cryptica has predominantly pyriform or utriform cystidia. Volvariella hypopithys has larger cystidia (46–124 × 9–30 µm) and vesiculose hyphae (25–120 × 23–108 µm) in the upper part of the pileipellis. All these taxa are molecularly quite distinct from V. pusilla , despite their overall morphological similarity.

Figures

FIGURE 4. Best tree from the Maximum Likelihood analysis of the ITS dataset of Volvariella: detailed view of the lineage including V. hypopithys and related taxa. BS ≥ 70 % and PP ≥ 0.90 are shown on or below the branches. Newly described taxa are highlighted in red.

FIGURE 16. Volvariella pusilla. A–D. Basidiomes. A. (SFC210825); B. (SFC190808); C. (GM1933); D. (LAP192). E–I. Microscopic characters (SFC190908). E. Cheilocystidia; F. Pleurocystidia; G. Spores; H. Pileipellis; I. Volva hyphae. Bar: (E–H) = 10 µm; (I) = 100 µm. Photos by F. Caballero (A–B, E–I), G. Muñoz (C), L.A. Parra (D).