A unique ballistosporic hypogeous sequestrate Lactarius from California.

Lactarius rubriviridis sp. nov., characterized 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 polyphyletic genera Arcangeliella and Zelleromyces, and an accounting of all known members of these genera are provided.