Early bloomer.  Five (5) white petals, yellow centers, resembles a Forget-Me-Not.  May release a purple dye, which the Maidu used for this purpose.  

Notes:  Borage family.  This plant can be distinguished from canyon nemophila, which also has small, white 5-petaled flowers, by its tall stem.  Also, the name popcorn describes its tendency to appear in clusters which resemble popcorn.  If you look very closely, you will see a 5-lobed washer at the center of each bloom (this is apparent in the second photo below).

Click on species name below to go to USDA for this plant

Kingdom Plantae -- Plants 
    Subkingdom Tracheobionta -- Vascular plants 
        Superdivision Spermatophyta -- Seed plants 
            Division Magnoliophyta -- Flowering plants 
                Class Magnoliopsida -- Dicotyledons 
                    Subclass Asteridae 
                        Order Lamiales 
                            Family Boraginaceae -- Borage family 
                                Genus Plagiobothrys Fisch. & C.A. Mey. -- popcornflower
                                    Species Plagiobothrys nothofulvus (Gray) Gray  
                                    -- rusty popcornflower