K. G. Ferris & Schoenig) G. L. Nesom, Phytoneuron 2013-80: 1. 2013.
Annuals, fibrous-rooted. Stems erect or slightly ascending from base, sometimes purplish, simple or few-branched from proximal nodes, 3–38 cm, glabrous. Leaves basal and cauline; petiole (proximal and proximal to mid cauline), distal bracteate or absent, ovate, margins entire; blade: divisions 1-veined, oblong-lanceolate to ovate in outline, 3–68 mm, slightly thickened, base (at proximalmost division) truncate, margins (of divisions) entire, bipinnately dissected, ca. 5–12(–15) primary divisions on each side, ultimate division nearly linear, apex obtuse to acute, surfaces glabrous. Flowers plesiogamous, 4–10(–12), on foreshortened distal nodes, usually clustered, chasmogamous, sometimes cleistogamous. Fruiting pedicels 6–14 mm, glabrous. Fruiting calyces urceolate to urceolate-campanulate, inflated, sagittally compressed, 8–11 mm, glabrous, throat closing. Corollas yellow, proximal lip sometimes red-splotched, palate ridges yellow, bilaterally symmetric, bilabiate; tube-throat cylindric-funnelform, 4–8 mm, exserted 0–2 mm beyond calyx margin or not; palate ridges densely villous. Styles glabrous. Anthers included, glabrous. Capsules included, 3–8 mm.
Phenology: Flowering Apr–Jun(–Sep).
Habitat: Slow-draining, ephemeral seeps on exfoliating granite slabs, over basalt.
Elevation: 300–1600 m.
Erythranthe filicifolia is known only from localities in Butte and Plumas counties.