Herbs, subshrubs, or shrubs, annual or perennial, terrestrial. Stems erect, terete, rarely 4-sided (D. pictus), glabrous, puberulent, hirtellous, hirsutulous, glandular-puberulent, or glandular-pubescent to glandular-villous with gland-tipped hairs. Leaves basal and cauline, or basal deciduous by flowering; petiole absent or present; blade not fleshy, leathery or not, margins toothed to subentire or entire, plane or revolute, venation palmate to subpinnate. Inflorescences axillary, flowers usually at medial to distal nodes, 0 or 1(or 2) in each axil, thus 1 or 2(–4) flowers at each node; bracts absent or present. Pedicels nearly absent or shorter than calyces, rarely ± equal to or slightly longer than calyces; bracteoles absent. Flowers erect to lateral or nodding, not strongly reflexed and appressed in fruit; sepals 5, calyx symmetric, tubular, lobes triangular to deltate, rarely reduced or barely evident, midvein angled or wing-angled; petals 5, corolla marcescent (caducous in D. mohavensis, D. pictus), blue, pink, red, magenta, lavender, purple, purplish brown, orange, or yellow, rarely white, sometimes multicolor, bilaterally symmetric, rarely radially symmetric, weakly to strongly bilabiate or not, rarely ± rotate, funnelform, or salverform, abaxial lobes 3, adaxial 2; stamens 4, didynamous, filaments glabrous or hairy; staminode 0; ovary 2-locular, placentation parietal; stigma 2-lobed. Fruits capsules, ovoid or asymmetrically ovoid to lanceoloid or nearly cylindric, sometimes longitudinally compressed, apex attenuate, walls smooth, eglandular, dehiscence loculicidal along both sutures at least 1/2 to base, indehiscent (species 29–38), or tardily dehiscent (D. pictus). Seeds 100–2000, yellow to olive green or dark brown, ovoid to oblong, flattened, wings absent. x = 8, 9, 10.


w United States, nw Mexico.


Species 49 (48 in the flora).

Diplacus includes western North American species with parietal placentation and pedicels usually distinctly shorter than the calyces, which were formerly treated within Mimulus in the broad sense. The closest relatives of Diplacus apparently are Mimetanthe and the Mexican-Central American Hemichaena Bentham, which also are characterized by parietal placentation. Diplacus has been divided into six sections (W. R. Barker et al. 2012; G. L. Nesom 2013b), corresponding to morphological patterns and cladistic patterns in the molecular-based phylogenetic analysis by P. M. Beardsley et al. (2004). The species are ordered here following that system as follows: sect. Eunanus (Bentham) G. L. Nesom & N. S. Fraga (species 1–27, type D. nanus), sect. Pseudoenoe (A. L. Grant) G. L. Nesom & N. S. Fraga (species 28, type D. pictus), sect. Cleisanthus (J. T. Howell) G. L. Nesom & N. S. Fraga (species 29–33, type D. douglasii), sect. Oenoe (A. Gray) G. L. Nesom & N. S. Fraga (species 34–38, type D. tricolor), and sect. Diplacus (species 39–48, type D. aurantiacus).

Evolutionary radiation in Diplacus has been restricted to the United States and Mexico, in contrast to Erythranthe, the other large segregate from Mimulus. The only species of Diplacus that does not occur in the United States is an endemic of Baja California on Cedros Island, D. stellatus Kellogg, a member of sect. Diplacus (M. C. Tulig and G. L. Nesom 2012). D. M. Thompson (2005) treated D. stellatus as a synonym of his broadly conceived D. aurantiacus.

A revision of Mimulus in the broad sense was provided by A. L. Grant (1924), followed by a major update and overview by F. W. Pennell (1951) that covered the majority of the western North American species of Diplacus. The present treatment closely follows that of D. M. Thompson (2005); a major area of taxonomic difference is in sect. Diplacus, where he treated most of the variation as within two species (D. aurantiacus and D. clevelandii), recognizing a number of varieties within D. aurantiacus that are here treated at specific rank. The detailed revision of Thompson forms a substantial basis of the treatment here.

Plants in sect. Diplacus are subshrubs or shrubs (except for the herbaceous Diplacus clevelandii) and are the only perennials (except for D. rupicola) in Diplacus. They also are distinctive in their glutinous, revolute-margined leaves, often with fascicles of smaller leaves in the axils of main shoots, and minutely glandular styles. Molecular data indicate that sect. Diplacus is derived from annual, herbaceous ancestors.


1 Subshrubs, shrubs, or herbs, perennial; leaf blade margins plane or revolute; calyces 17–40 mm. > 2
2 Herbs, rhizomatous; corollas bright golden yellow. Diplacus clevelandii
2 Subshrubs or shrubs, not stoloniferous or rhizomatous; corollas red, maroon, scarlet, orange-red, orange, pale orange, dull orange, pale yellow-orange, cream, yellow, pale yellow, or nearly white, sometimes golden yellow (D. aridus). > 3
3 Corollas red, scarlet, orange-red, orange, or maroon. > 4
4 Calyces glandular-puberulent and short glandular-villous to hirsute-villous. Diplacus rutilus
4 Calyces glabrous. > 5
5 Leaf blades linear-oblong or narrowly elliptic to narrowly lanceolate or oblanceolate, apices acute; corolla limbs 15–23 mm diam. Diplacus puniceus
5 Leaf blades elliptic to broadly elliptic-oblanceolate or elliptic-lanceolate, apices acute to obtuse or rounded; corolla limbs 12–16 mm diam. Diplacus parviflorus
3 Corollas pale yellow, yellow, golden yellow, light orange, pale yellow-orange, orange, orange-yellow, dull orange, cream, or nearly white. > 6
6 Abaxial leaf surfaces hairy. > 7
7 Calyces glabrous or hirtellous and/or minutely stipitate-glandular; leaf blade surfaces glabrous or abaxial usually sparsely to densely hairy, hairs branched, adaxial usually without unbranched hairs. Diplacus aurantiacus
7 Calyces densely glandular-puberulent or glandular-pubescent to short glandular-villous or hirsute-villous; leaf blade abaxial surfaces moderately villous, hairs unbranched, vitreous or densely hairy, hairs branched, adaxial glabrous or glabrescent. > 8
8 Corollas usually pale yellow or cream to yellow, limbs 20–30 mm diam.; calyces 28–40 mm; leaf blade abaxial surfaces moderately villous, hairs unbranched, vitreous. Diplacus calycinus
8 Corollas light orange to pale yellow-orange, limbs (25–)28–40 mm diam.; calyces 22–32 mm; leaf blade abaxial surfaces densely hairy, hairs branched. Diplacus longiflorus
6 Abaxial leaf surfaces glabrous. > 9
9 Corolla lobes entire; calyces 35–40 mm, tubes distinctly dilated distally; stems 80–330 mm. Diplacus aridus
9 Corolla lobes apically incised 1/4–1/2 length, appearing 2-lobed; calyces 20–30 mm, tubes slightly dilated distally; stems 300–800(–1200) mm. > 10
10 Leaf blades elliptic or oblong-elliptic to elliptic-lanceolate or elliptic-oblanceolate, 4–17 mm wide; corolla limbs 30–45 mm diam.; c Sierra Nevada. Diplacus grandiflorus
10 Leaf blades narrowly elliptic to narrowly lanceolate or narrowly elliptic-oblong, 3–9 mm wide; corolla limbs 20–25 mm diam.; coastal counties. Diplacus linearis
1 Herbs, annual, rarely perennial (D. rupicola); leaf blade margins plane; calyces usually 2–18 mm, (6–)9–25(–31) mm in D. bolanderi, D. brevipes, D. traskiae, and D. tricolor. > 11
11 Herbs, perennial; calyx lobes unequal; corolla limbs pinkish white to nearly white. Diplacus rupicola
11 Herbs, annual; calyx lobes subequal or unequal; corolla limbs not pinkish white to nearly white. > 12
12 Corollas salverform-rotate, throats dark purplish brown without internal or external markings, palate ridges absent. > 13
13 Corolla lobes purplish brown basally with red veins; leaf blades narrowly elliptic to elliptic-lanceolate, margins entire; stems terete; stigma lobes subequal. Diplacus mohavensis
13 Corolla lobes white with purplish brown veins; leaf blades elliptic to elliptic-ovate or obovate, margins crenate; stems 4-sided; stigma lobes unequal. Diplacus pictus
12 Corollas bilabiate, sometimes not, throats whitish, yellow, pink, magenta, red, or purple, palate ridges present, sometimes absent (D. congdonii). > 14
14 Corollas yellow or predominantly yellow, sometimes with red, reddish, reddish brown, maroon, or purple spots or lines. > 15
15 Calyces (7–)10–25(–31) mm; corolla tube-throats (10–)15–30(–34) mm; leaves 7–90(–125) mm. Diplacus brevipes
15 Calyces (3–)5–14 mm; corolla tube-throats 5–23 mm; leaves 2–30(–55) mm. > 16
16 Stems 5–15(–20) mm; leaf blade margins usually ciliate along proximal 1/2; corolla tube-throats 5–10 mm. Diplacus pygmaeus
16 Stems 10–200(–240) mm; leaf blade margins not ciliate; corolla tube-throats (8–)10–23 mm. > 17
17 Flowers 1 per node. Diplacus vandenbergensis
17 Flowers 2 per node, or 1 or 2 per node on 1 plant. > 18
18 Stigmas exserted or at opening of corolla tube-throat. Diplacus mephiticus
18 Stigmas included. > 19
19 Calyx lobes subequal; corolla throats with dark maroon stripes; s Sierra Nevada, (1200–)1500–3300 m. Diplacus bicolor
19 Calyx lobes unequal; corolla throats usually with 6–8 narrow reddish spots or lines in arc on abaxial lip around mouth and throat floor with reddish spots, colored palate ridges; Mohave Desert, (600–)800–1700(–1800) m. Diplacus parryi
14 Corollas shades of red to purple, sometimes white or magenta with yellow abaxial lobes or palate. > 20
20 Corolla lips: abaxial essentially absent or smaller than adaxial; calyces distinctly asymmetrically attached to pedicels. > 21
21 Corolla lips: abaxial absent or nearly absent. Diplacus douglasii
21 Corolla lips: abaxial present, usually smaller than adaxial. > 22
22 Calyces 18–21 mm; Santa Catalina Island. Diplacus traskiae
22 Calyces 5–16(–17) mm; Santa Catalina and Santa Cruz islands (D. brandegeei) or mainland. > 23
23 Palate ridges absent or purple; corolla throats not golden yellow at base. Diplacus congdonii
23 Palate ridges golden yellow; corolla throats golden yellow at base. > 24
24 Corolla limbs 10–18 mm diam.; pedicels usually twisting, inverting calyx in fruit; leaf margins not ciliate; California (mainland) and Oregon. Diplacus kelloggii
24 Corolla limbs 5–11 mm diam.; pedicels not twisting, inverting calyx in fruit; leaf margins usually ciliate in proximal 1/2; California (Santa Catalina and Santa Cruz islands). Diplacus brandegeei
20 Corolla lips: abaxial and adaxial of ± equal size; calyces symmetrically, sometimes slightly asymmetrically, attached to pedicels. > 25
25 Plants acaulescent or short-caulescent; stems 30–70 mm; basal leaves densely clustered; corolla tube-throats 15–60 mm. > 26
26 Corollas not bicolored or tricolored (throat and limb usually magenta to purple with a dark maroon-purple spot or elongate blotch at base of each abaxial lobe, palate ridges and bases of abaxial lips yellow). Diplacus angustatus
26 Corollas bicolored or tricolored. > 27
27 Corollas bicolored. Diplacus pulchellus
27 Corollas tricolored. Diplacus tricolor
25 Plants caulescent; stems 10–900(–1200) mm; basal leaves seldom densely clustered; corolla tube-throats 6–30 mm. > 28
28 Leaf blade apices (at least distal leaves) abruptly acuminate or cuspidate to long-tapering or long-acuminate. > 29
29 Corollas not bilabiate; calyces inflated in fruit, lobes strongly unequal. Diplacus bigelovii
29 Corollas bilabiate; calyces not inflated in fruit, lobes subequal or slightly unequal. > 30
30 Leaf surfaces glabrous or sparsely glandular-puberulent, or adaxial minutely stipitate-glandular. > 31
31 Corolla tube-throats 13–16(–19) mm, limbs 16–24 mm diam.; leaves (10–)15–25(–35) mm; Malheur County, Oregon, and Ada and Owyhee counties, Idaho. Diplacus cusickii
31 Corolla tube-throats 8–12 mm, limbs 10–16 mm diam.; leaves 10–15(–25) mm; Crook, Deschutes, Jefferson, Klamath, Lake, and Wheeler counties, Oregon. Diplacus deschutesensis
30 Leaf surfaces densely glandular-villous. > 32
32 Stems (10–)30–240(–350) mm, usually simple or few-branched; calyces 7–12 mm; corolla tube-throats 13–16(–19) mm, limbs 14–26 mm diam.; capsules 10–17 mm; California, Idaho, Oregon, Washington. Diplacus cusickioides
32 Stems 20–140 mm, usually many-branched; calyces 7–9(–10) mm; corolla tube-throats 9–11 mm, limbs 12–15 mm diam.; capsules 6–8 mm; Nevada. Diplacus ovatus
28 Leaf blade apices rounded, rounded-acute, obtuse, or acute. > 33
33 Capsules indehiscent; corolla lobes each with discrete, dark spot at base; flowers 1 per node. Diplacus tricolor
33 Capsules dehiscent; corolla lobes not each with discrete, dark spot at base; flowers 1, 2, or 1 or 2 per node on 1 plant. > 34
34 Flowers 1 per node. > 35
35 Corolla tube-throats 7–10 mm, limbs 4–7 mm diam. Diplacus rattanii
35 Corolla tube-throats 9–23 mm, limbs 8–26 mm diam. > 36
36 Corollas: palate ridges yellow, throat floor glabrous or puberulent at mouth. Diplacus fremontii
36 Corollas: palate ridges white or yellow fading distally to white, throat villous at mouth. > 37
37 Corolla lobes with dark red-purple midveins extending from throat, lobes not each with dark spot at base, throat ceilings glabrous; styles glandular-puberulent; abaxial stigma lobes 1.5 times adaxials. Diplacus viscidus
37 Corolla lobes without dark midveins, lobes dark at base, throat ceilings villous-pilose; styles glabrous or sparsely eglandular-puberulent; abaxial stigma lobes 3–4 times adaxials. Diplacus compactus
34 Flowers 2 per node, or 1 or 2 per node on 1 plant. > 38
38 Stigmas exserted or at opening of corolla tube-throats. > 39
39 Corolla limbs not bilabiate; anthers glabrous. > 40
40 Corollas: palate ridges and throat floors yellow, throats usually with large dark spot on each side of mouth on lateral walls; stigma lobes equal; calyces not inflated in fruit, ribs inconspicuous. Diplacus johnstonii
40 Corollas: palate ridges or throat floors white, throats without dark spots; stigma lobes unequal, abaxials 2–3 times adaxials; calyces inflated in fruit, ribs prominent. Diplacus bolanderi
39 Corolla limbs bilabiate, rarely not; anthers hairy. > 41
41 Leaf blade margins crenate to serrulate, at least on biggest leaves; pedicels 2–7(–10) mm in fruit. Diplacus clivicola
41 Leaf blade margins entire; pedicels 1–3 mm in fruit. > 42
42 Corolla limbs 5–7 mm diam., tube-throats 7–10 mm, tubes 0.8–1.2 mm diam. at filament insertion; capsules 4–6 mm. Diplacus jepsonii
42 Corolla limbs (5–)7–14(–15) mm diam., tube-throats 8–14(–15) mm, tubes 1.1–1.9 mm diam. at filament insertion; capsules 5–12 mm. > 43
43 Leaf surfaces glandular-pubescent and (at least along veins) viscid-villous. Diplacus mephiticus
43 Leaf surfaces minutely glandular-puberulent. > 44
44 Distal leaves: blades oblanceolate to elliptic-lanceolate, 2–4 mm wide; corolla tube-throats 11–15 mm, throat floors villous with hairs extending onto adaxial lip; capsules 8–12 mm. Diplacus nanus
44 Distal leaves: blades obovate to broadly oblanceolate, 5–8(–12) mm wide; corolla tube-throats 8–10 mm, throat floors glabrous; capsules 5–8(–9) mm. Diplacus cascadensis
38 Stigmas included. > 45
45 Stems glandular-puberulent; calyx lobes unequal, adaxial longer. Diplacus parryi
45 Stems glandular-puberulent to glandular-pubescent or glandular-villous, sometimes glabrous or glabrate proximally; calyx lobes subequal. > 46
46 Corolla tube-throats 6–8 mm, limbs 3–5 mm diam. Diplacus leptaleus
46 Corolla tube-throats (8–)9–22(–25) mm, limbs 6–24 mm diam. > 47
47 Calyx lobes shallowly triangular to broadly ovate; herbage not drying dark. Diplacus torreyi
47 Calyx lobes triangular or narrowly triangular; herbage usually drying dark. > 48
48 Calyx tubes not strongly plicate, ribs thin, not strongly raised. Diplacus bicolor
48 Calyx tubes strongly plicate, ribs thickened, strongly raised. > 49
49 Nodes 4–15(–20); calyx ribs narrow, intercostal areas green to purple, not membranous. Diplacus graniticola
49 Nodes 3–6; calyx ribs broad, intercostal areas whitish, membranous. > 50
50 Calyces not inflated in fruit; abaxial stigma lobes 1.5 times adaxial. Diplacus layneae
50 Calyces inflated in fruit; stigma lobes equal to subequal. > 51
51 Leaf apices abruptly acuminate, acute-acuminate, or cuspidate to long-tapering or long-acuminate. Diplacus bigelovii
51 Leaf apices acute or rounded. > 52
52 Stems and leaves glandular-puberulent; corolla tube-throats 10–14 mm, limbs 6–10 mm diam.; palate ridges yellow. Diplacus thompsonii
52 Stems glandular-villous; corolla tube-throats (10–)13–22(–25) mm, limbs 14–23 mm diam.; palate ridges white. Diplacus constrictus
... more about "Diplacus"
Guy L. Nesom +  and Melissa C. Tulig +
Nuttall +
Sessile monkeyflower +
w United States +  and nw Mexico. +
Greek dis-, two, and plakos, placenta, alluding to splitting of capsule into valves bearing parietal placentae +
Ann. Nat. Hist. +
ezell1971a +, mcminn1951a +, michener1983a +, tulig2000a +  and tulig2012a +
Eunanus +  and Mimulus sect. Diplacus +
Diplacus +
Phrymaceae +