[Wikipedia] Description, Conservation, Rarity: It is endemic to Marin County, California, where it is known only from one population on Ring Mountain east of Mill Valley. There it occurs on a single serpentine outcrop in grasslands from 50–150 metres (160–490 ft) in elevation.[2][3] Conservation The plant was federally listed as a threatened species in 1995. It is considered threatened due to loss of surrounding habitat to recreational activities, to competition from invasive plant species, to its proximity to a dense population center, and to its confinement to a single population of plants. The population grows on land owned by the Marin County Open Space District,[7] an area previously owned and preserved by The Nature Conservancy.[6] It was first brought to the attention of science in 1971, and was described to science in 1973.[8] It is protected along with a number of other rare serpentine soils endemic plants that grow on and around Ring Mountain.[6][5] The plant has probably always been rare and limited to its current distribution on the Ring Mountain outcrop.[6] A 1991 estimate placed the total population size at about 40,000 individuals.[6][1] While the land is protected, the flora upon it are still vulnerable to events such as wildfires or drought, and to damage from off-leash dogs, hikers, cyclists, vandals, and wildflower collectors.[6] (link added by Mary Ann Machi)