[Wikipedia] Achene Information: Calendula arvensis produce three types of achenes (fruits of the sunflower family), they are rostrate, cymbiform and annular. Rostrate and cymbiform are suitable for long-distance diffusion, because they have larger size and weight than annular, while annular is suitable for short-distance diffusion. (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).