Subshrubs. Stems erect, 300–800(–1200) mm, minutely hirtellous to hirsutulous with slightly deflexed, eglandular hairs. Leaves cauline, relatively even-sized; petiole absent; blade narrowly elliptic to narrowly lanceolate or narrowly elliptic-oblong, 12–37 × 3–9 mm, margins entire, serrulate, or mucronulate, plane or revolute, apex usually obtuse to rounded, surfaces glabrous. Pedicels 3–10 mm in fruit. Flowers (1 or)2 per node, chasmogamous. Calyces not inflated in fruit, 20–28 mm, glabrous, tube slightly dilated distally, lobes unequal to subequal, apex acute. Corollas yellow-orange to dull orange, not spotted or striped, palate ridges yellow, tube-throat 35–45 mm, limb 20–25 mm diam., bilabiate, lobes oblong, each apically incised 1/4–1/2 length, appearing 2-lobed. Anthers included, glabrous. Styles minutely glandular. Stigmas included, lobes equal. Capsules 18–30 mm. 2n = 20.
Phenology: Flowering Apr–Jun.
Habitat: Dry hillsides, rock outcrops.
Elevation: 100–300 m.
The coastal Diplacus linearis (as Mimulus bifidus subsp. fasciculatus) was allied by F. W. Pennell (1947) with the Sierran D. grandiflorus (as M. bifidus subsp. typicus) as a narrower-leaved and smaller-flowered subspecies; see discussion concerning its distribution under 40. D. grandiflorus. The two were considered synonymous by D. M. Thompson (2005). They are distinct in geography, ecology, and morphology.