What You Should Know
Russula claroflava is a basidiomycete mushroom of the genus Russula. It is found in wet places under birch and aspen woodlands across Europe and North America. It has a yellow cap, white gills and stipe and bruises grey. It is mild-tasting and regarded as good to eat.
The Russula family split from other mushrooms, evolutionarily, many years ago and have round cells instead of most other living organisms which have elongated cells, this gives Russulas the common name Brittlegills as the cells make the mushroom brittle.
Other names: Yellow Swamp Russula, Yellow Swamp Brittlegill, Gulkremla (Sweden), Dzeltenā bērzlape (Latvia).
Russula claroflava Mushroom Identification
Mycorrhizal with various species of birch, and with red spruce and Fraser fir; growing scattered or gregariously; summer and fall; northern and montane Europe and North America.
3–6 cm; convex when young; becoming broadly convex or nearly flat; tacky to sticky when fresh and young, but soon dry; medium yellow; with age staining gray near the margin; the margin becoming slightly lined; the skin peeling easily about halfway to the center.
Narrowly attached to the stem; close; without short-gills; white when young but soon becoming yellow as the spores mature; discoloring gray with age.
3–6 cm long; 1–1.5 cm thick; equal; dry; bald; white, bruising and discoloring gray; hollowing with age; basal mycelium white.
White; staining and aging slowly gray.
KOH negative on cap surface. Iron salts negative or slightly pink on the stem surface.
Spores 7–10 x 6–9 µm; subglobose or broadly ellipsoid; ornamentation 0.5–1 µm high, as mostly isolated amyloid warts and occasional connecting lines. Macrocystidia 25–40 x 5–10 µm; fusiform, occasionally with a mucro; smooth; thin-walled; yellowish in KOH. Pileipellis an ixocutis; elements 2–5 µm wide, hyaline and smooth in KOH; primordial hyphae present, often encrusted.
Russula ochroleuca has an ochre-yellow cap, often greening slightly in the middle; it has fairly hot, peppery flesh.
Russula claroflava Taxonomy and Etymology
The Yellow Swamp Brittlegill mushroom was described in 1888 by British mycologist William Bywater Grove (1838 - 1948), who gave it the binomial scientific name Russula claroflava which mycologists still use today when referring to this species. Born in Birmingham, England, Grove is perhaps most famous for his translation into English of the mycological treatise of Louis Rene and Charles Tulasne: Selecta Fungorum Carpologia (3 volumes, 1861-1865).
Synonyms of Russula claroflava include Russula constans Britzelm., Russula decolorans var. constans (Britzelm.) P. Karst.
Russula, the generic name, means red or reddish, and indeed many of the brittlegills have red caps (but many more are not, and several of those that are usually red can also occur in a range of other colors!). The specific epithet claroflava comes from clar- meaning brilliant or bright, and -flava meaning yellow. Bright yellow is a very good description of the caps of the Yellow Swamp Brittlegill.
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