[Wikipedia] taxonomy: In 1856, John Torrey described Trillium sessile var. angustipetalum based on a specimen collected by John Milton Bigelow two years earlier in California. In 1975, John Daniel Freeman described the species Trillium angustipetalum based on Torrey's variety. The epithet angustipetalum means "narrow-petaled". (link added by Mary Ann Machi)
Calflora:
Information on California plants for education, research and conservation,
with data contributed by
public and private institutions and individuals.
[web application]. 2025.The Calflora Database
[a non-profit organization].Available:
https://www.calflora.org/(Accessed: 03/28/2025).
