Summary:
Clitocybe rivulosa is distinguished by small size, dingy grayish-white color, close decurrent gills, mild odor, growth in grass, and white spore print. |The cap surface is "dull or shiny, glabrous and opaque or at times slightly canescent and with watery pale buff areas or spots, at times subzonate but not rivulose or rimose" (Bigelow). |Clitocybe rivulosa might be the best name for what has been known as Clitocybe dealbata in the Pacific Northwest, although a strong case can be made for the names Clitocybe sudorifica or C. dealbata (Fr.) P. Kumm. ssp. sudorifica (Peck) Bigelow. The latter is the basis for the description below, which Bigelow says is quite common in the Pacific Northwest. He says that there are two taxa in Europe that have been referred to as C. dealbata, the first with a bald, smooth cap and no distinct odor and the second with a canescent cap and a farinaceous odor. He rejects the first taxon for the North American mushroom on the basis that it can at times be slightly canescent and with watery pale buff areas: "in fresh condition neither the wet nor dry forms have the surface of the Scandinavian C. dealbata [Latin italicized]". He rejects the second taxon on the basis that the North American mushroom does not have a farinaceous odor. Peck described C. dealbata var. sudorifica then C. sudorifica on the basis of the sweat-inducing properties, which does not seem to Bigelow enough to justify species status (especially since sudorific properties are described for Clitocybe dealbata). |However, the online Species Fungorum, accessed January 24, 2017, gives C. sudorifica Peck as the current name for the mushroom Bigelow is describing. MycoBank, on the other hand gives Clitocybe rivulosa (Pers.) Kumm. as the current name. Bigelow comments (with Latin names italicized) ''Sometimes the North American taxon has been called C. rivulosa, but this is an improper use of this epithet, as Fries (1821) clearly describes the pileus of A. rivulosus as "glaber" even though "demum rimoso-rivuloso." '' [''demum'' means approximately ''finally'']. Nevertheless, two recent field guides, Desjardin(6) and Siegel(2) follow MycoBank in using the name Clitocybe rivulosa. The former says that Clitocybe dealbata (Sowerby) Gillet and Clitocybe sudorifica (Peck) Peck are misapplied names. |Alvarado(2) provide further input, "Similarly Clitocybe rivulosa and C. dealbata are sometimes regarded as synonyms, despite the fact that C. rivulosa was described from forest soil and C. dealbata first reported in herbaceous habitats. In addition, concentric rings of the cracked cuticle can develop with age on the pileus of C. rivulosa, but these are apparently absent from C. dealbata. The latter is also smaller, 2-3(4)cm, in contrast to 4-5(7)cm of C. rivulosa (Clemencon 1984, Bon 1997). Kuyper (1995) states that both species can be present in forests, but differ from C. phyllophila/C. cerussata because of their smaller habit and more decurrent lamellae." (Alvarado(2) with Latin names italicized and spaces before the centimeter unit, Clemencon with acute accent on first e and cedilla on c, hyphens used differently).

Gills:
adnate to decurrent, close; grayish white to buff or pinkish buff, (Arora), adnate, soon short-decurrent to decurrent, crowded or close, narrow to moderately broad, up to 0.4cm broad; whitish then dingy pale buff (usually somewhat darker than cap), (Bigelow)

Stem:
1-4cm x 0.2-0.7cm, equal or slightly thicker at either end, rather tough; colored like cap, smooth, (Arora), 1-3(5)cm x 0.25-0.5cm at top, equal or widened slightly at the base, solid becoming hollow, often curved, eccentric and/or compressed [flattened] at times; whitish or becoming buff when old and when fibrils appressed; with thin fibrillose coating, becoming bald, base white-mycelioid and sometimes a few white rhizomorphs, (Bigelow)

Veil:
[presumably none]

Odor:
mild (Arora, Bigelow)

Taste:
mild (Bigelow)

Microscopic spores:
spores 4-5.5 x 2-4 microns, elliptic, smooth, (Arora), spores (3)4-4.5(5.5) x 2-3(3.5) microns, elliptic, smooth, inamyloid, cyanophobic; basidia 4-spored, 15-24 x 4-5.5 microns; [pleurocystidia and cheilocystidia presumably absent]; cap cutis of hyphae 1.5-3.5 microns wide, cylindric; clamp connections present, (Bigelow), cap cuticle of +/- parallel colorless hyphae 2-4 microns wide, in part covered with fine granules, hyphae toward the trama 5-10 microns wide, all septa with clamp connections, (Breitenbach)

Spore deposit:
white or rarely creamy (Arora)

Notes:
Collections were examined from WA, OR, NS, ON, QC, YT, CA, CO, CT, MA, ME, MI, MS, NY, OH, RI, TN, TX, VT, Denmark, Norway, and Sweden, (Bigelow). Clitocybe rivulosa is found also in BC (Bandoni(1) (as C. dealbata)).

EDIBILITY

poisonous and potentially fatal to children (muscarine producing profuse sweating, salivation, diarrhea, etc.), (Arora)

Synonyms and Alternate Names:
Clitocybe dealbata sensu auct. mult