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Species Information
Summary: Features include 1) growth on Russula species and occasionally Lactarius, covering deformed gills and often the stem, sometimes the cap, turning the fruitbody firm, 2) color that is yellow or green, 3) large unicellular spores, 4) a peculiar anatomy of the perithecial apex ("distinctive for the moniliform chains of cells that extend from the surface of the papilla"), and 5) no anamorph known in nature. It should not be eaten (Lincoff). It is common in wet weather wherever the host species are found, throughout many parts of North America, (Phillips).
It is widespread in north temperate regions, occurring in BC, WA, OR, ID, AB, MB, NB, NS, PQ, AK, AZ, CO, CT, FL, GA, OH, MA, MD, ME, MI, MT, NC, NH, NJ, NM, NY, OH, PA, RI, SC, TN, TX, UT, VA, VT, WI, WV, Czechoslovakia, Denmark, Estonia, France, Finland, Germany, Norway, Russia, Spain, Sweden, Switzerland, United Kingdom, and Japan, (Rogerson). It also occurs CA (Castellano) and in Ukraine and Kazakhstan, (Poldmaa).
Fruiting body: subiculum "at first yellowish to bright yellow, then yellowish green to dark green, finally blackish green"; perithecia "yellow when fresh, olivaceous to blackish when dry, usually darker than the surrounding subiculum, immersed except for papilla", (Rogerson), subiculum "profuse, first yellow or green when old", not changing color in KOH, texture hyphal; perithecia "formed all over the subiculum, caespitose, immersed in the subiculum except the papilla", at first yellow, becoming green when mature, KOH reaction absent, (Poldmaa), "first yellow, then yellow-green to green, finally black-green", (Castellano), white at first, but eventually becomes light olive-green as spores mature, (McKnight)
Microscopic: SPORES 32-35 x 4.5-5.5 microns, fusiform to naviculate, nearly smooth to prominently verrucose and apiculate (verrucae up to 1 micron high, "apiculi 2.4-7.3 microns long, acute, straight or curved and sometimes hooked"), one-celled; ASCUS 160-200 x 5-8 microns, filiform to long cylindric, "apex thickened and with a pore"; PERITHECIUM 380-485 x 180-290 microns, broadly ovate to obpyriform, immersed except for papilla, papilla 96-120 microns high, 180-230 microns wide at apex, truncate or obtuse, KOH-, perithecial wall about 25 microns wide laterally, of hyphae 3-4 microns wide, sinuous, with nonpigmented walls, perithecial apex composed "of hyphae constricted at septa and appearing moniliform with cells 5-7 microns long, 4-5 microns wide" and walls < 0.5 microns thick, "hyphae tending to separate from each other"; subicular hyphae 3-5.5 microns wide, "much branched, septate, much entangled, remaining filamentous", "hyphae at the surface with many 3 microns wide free ends and short cells with constrictions at the septa" and mimicking the hyphae of the perithecial apex, KOH-, (Rogerson), SPORES (27)30-36 x 4.5-5.5(6.5) microns, fusiform, aseptate, "finely verrucose, verrucae arranged uniformly, 1 micron high, ends apiculate", apiculi 2.5-7 microns long, with acute tips; ASCUS 160-200 x 5-8 microns, "with apex thickened, penetrated by a pore"; PERITHECIUM 380-480 x 180-290 microns, "immersed in the subiculum except the papilla", perithecial wall 25 microns wide, perithecial papillae 95-120 microns high, tip obtuse, "of hyphal texture, with cells not forming differentiated regions"; subiculum cells 3-5.5 microns wide, not swollen; anamorph in nature not observed, (Poldmaa)
Habitat / Range
on Russula species, covering the deformed gills and often the stem, sometimes spreading to the top of the cap of the host, (Rogerson), growing on fruitbodies of Russulales: Russula spp., also reported on Lactarius; covering host spore-bearing surface and upper stem; host fruitbodies turn firm, (Poldmaa), fruiting July through November (Castellano)
Similar Species
The Hypomyces species that parasitize members of the Russulaceae can be distinguished by color when mature, but several species are somewhat yellow when immature: these taxa and their color when mature include Hypomyces lactifluorum (orange), H. lateritius (ochraceous to brick red to red-black), H. macrosporus (white to pale tan), H. banningiae Peck from MA, MD, NC, NJ, NY, PA, SC, VA (white to pale tan), H. lithuanicus T. Heinrichson-Normet from ON, CT, MI, NY, WI, Europe (cream-ocher to cinnamon), and H. petchii G. Arnold from New Zealand (apricot), (Castellano, but distribution from Poldmaa(2) and Rogerson (3)).
