Photo: Diane Edwardson, May 20, 2015. Spanish Lotus (Acmispon americanus) is a tiny wildflower that varies from white to more pinkish, growing on the trail on the north end of the Red Car Property. (Click on photos to enlarge.)
It tends to grow near the edges of the path, often where the California Harvester Ants are active. Sounds like they have a symbiotic relationship. The flowers are an annual and must reseed themselves to grow the following year. The ants till the soil and most likely store some of the seeds too.
Photo: Diane Edwardson, May 20, 2015. How tiny are the Spanish Lotus flowers? About 1/4 of an inch or less. For scale, if you look closely, the dry weeds in the above photo are foxtails (the dry weeds that get stuck up your dog's nose, in his ears and in between his toes).