148 Mycologia, 95(1), 2003, pp. 148–155. q 2003 by The Mycological Society of America, Lawrence, KS 66044-8897 A unique ballistosporic hypogeous sequestrate Lactarius from California Dennis E. Desjardin 1 Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California 94132 Abstract: Lactarius rubriviridis sp. nov., character- ized by hypogeous, sequestrate basidiomes with red latex, green stains, and forcibly discharged, reticulate basidiospores is described and illustrated. During the Spring, the new species forms basidiomes associated with conifers at 1400–1800 m elevation in the Sierra Nevada, and is known from two specimens collected 19 yr apart. Comparisons with the putatively polyphy- letic genera Arcangeliella and Zelleromyces, and an ac- counting of all known members of these genera are provided. Key Words: Arcangeliella, astrogastraceous series, Russulales, Zelleromyces INTRODUCTION In June 1982, an unusual and exciting new species of hypogeous sequestrate fungi was collected by Mrs. Dorothy Zediker at Foresta Campground in Yosemite National Park, California. Fresh material was ob- tained by Dr. Harry Thiers and Herb Saylor (then a student of Dr. Thiers) at San Francisco State Univer- sity where they immediately recognized the material (HS 921) as representing a new species belonging to the astrogastraceous series of Russulales. Dr. Thiers and Mr. Saylor intended to publish the new species as ‘‘Zelleromyces rubriviridis’’ (currently a nom. herb.), and they submitted a formal description in a manuscript to Mycologia in 1986. Favorable reviews were received, but there were unresolved discussions regarding subgeneric classification. The new species name was never validly published, and the single specimen languished in SFSU. Recently, fresh mate- rial of the species (DED 7312) was collected from a similar habitat at a similar elevation during the same time of year, but from a site approx 130 miles farther north in the Sierra Nevada. The new material provid- ed further details on macromorphology, distribution, and ecology, and for the first time displayed convinc- Accepted for publication June 18, 2002. 1 Email: ded@sfsu.edu ingly the ballistosporic nature of the gastroid basidi- omes, a feature that is unusual among hypogeous Russulales. The new species is described below and accepted in the genus Lactarius subgenus Dapetes. Color terms and notations are from Kornerup and Wanscher (1978). Lactarius rubriviridis Desjardin, Saylor et Thiers, sp. nov. FIGS. 1–4 Gastrocarpia 25–60 mm diametro, 20–45 mm alta, irre- gulatim globosa vel ellipsoidia, fusca vel rubrofusca, tactu viridescens, alveolata. Peridium nullum maturitate. Gleba lacunosa, subflavida, tactu viridescens. Contextus virides- cens ubi contusus. Latex parcus, laete ruber. Stipe-columel- la nulla. Columella praesens, conspicua. Odor et sapor haud distinctus. Basidiosporae (8–) 8.5–11 3 (7–) 7.5–8.5 mm, ellipsoideae, reticulatae vel partiale reticulatae, ballis- tosporae, amyloideae. Trama hymenophoris hyphis filamen- tosis, sphaerocystis nullus. Peridiopellis nullus. In solo sub- ter arboribus coniferis. Holotypus hic designatus: DED 7312 (SFSU), legit D. E. Desjardin, 14 June 2001, prope Cold Creek Campground, Sierra Co., California, USA. Basidiomes (FIGS. 1–2) hypogeous, 25–60 mm long 3 20–45 mm broad 3 15–30 mm thick, irregularly globose to ovoid or ellipsoid, sometimes lobed. Perid- ium absent, exterior surface alveolate to ridged and pitted from exposed locules and hymenophoral tra- mal tissue; ridges reddish brown to dark brown (8– 9E–F5–7), staining deep greenish grey to bluish green or dark green (25–27F5–7) where bruised. Gle- ba loculate; locules irregular in shape, often elon- gate, 1–5 mm 3 0.5–1.5 mm, filled with yellowish white to orangish white (4–5A2) or cream-colored (4A3) basidiospores at maturity; hymenophoral tramal tissue firm, waxy, white to yellowish white (4A2), but becoming reddish brown (9D7–8) when cut from ex- uded latex; columella rudimentary to well-developed, composed of radiating dendritic veins arising from a central main vein 1–4 mm diam, initially white, but staining greenish white (27A2–3) to greyish green (26C6–7) over time when cut. Latex scant, deep red (9B–C7–8), discoloring tramal tissue to dark brown- ish red (11–12E7–8). Odor not distinctive or sweet. Taste mild. Spores forcibly discharged, leaving an or- angish white (5A2) to yellowish white (4A2) or cream (4A3) deposit. Basidiospores (FIG. 3) (8–) 8.5–11 3 (7–) 7.5–8.5 mm(x¯ 5 9.8 6 0.7 3 7.8 6 0.4 mm, Q 5 1.1–1.4, Q ¯ 5 1.26 6 0.06, n 5 25 spores per 2 specimens), ovoid