Erythranthe willisii
Phytoneuron 2017-17: 7, figs. 14–22. 2017.
Perennials, rhizomatous, rarely rooting at proximal nodes, usually forming large colonies, rhizomes white, usually highly branching. Stems usually sprawling-decumbent, branched, sometimes simple, 7–45 cm, nodes (2–)4–15+, densely glandular-villous, hairs 1–2 mm, glandular, internodes evident. Leaves usually cauline, basal not persistent, distinctly separated; petiole 0 mm, sometimes 1–2 mm at proximal nodes; blade bicolored, purplish abaxially, pinnately veined, ovate to elliptic-ovate, midcauline 10–35 × 6–18 mm, base rounded to subcordate, margins coarsely serrate-dentate to denticulate or subentire, apex short-attenuate to acute, obtuse, or rounded, surfaces densely glandular-villous, hairs 1–2 mm, gland-tipped. Flowers herkogamous, (4–)8–30+, from medial to distal nodes, sometimes from all nodes. Fruiting pedicels 4–20(–25) mm, densely glandular-villous, hairs 1–2 mm, gland-tipped. Fruiting calyces ridge- to wing-angled, campanulate to cylindric-campanulate, weakly inflated, 7–10 mm, densely glandular-villous, lobes erect to slightly spreading, unequal, triangular to linear-lanceolate, 2–4 mm, apex acuminate-apiculate. Corollas yellow, throat, tube, and proximal portion of abaxial 3 lobes with fine, red to brownish lines, weakly bilaterally or nearly radially symmetric, weakly bilabiate or nearly regular; tube-throat narrowly funnelform, 12–15 mm, exserted beyond calyx margin; limb 9–12 mm wide (pressed), lobes oblong-obovate, apex rounded to notched. Styles glabrous. Anthers included, glabrous or finely hirtellous to scabrous. Capsules included, 4–5 mm.
Phenology: Flowering May–Sep.
Habitat: Seepage, drainage margins, moist soils, talus, cracks and crevices, soils deprived from serpentine.
Elevation: (500–)700–900 m.
Discussion
Erythranthe willisii is narrowly endemic over serpentine along the North Fork Feather River (including the North Branch) in Plumas County. In the original description, its range was said to include serpentine localities in closely adjacent areas of east-central Butte, Plumas, and northwestern Yuba counties, but subsequent field work has shown that these peripheral populations are E. moschata, and that E. willisii occurs only in the bottom of the Serpentine Canyon area. The most consistent and recognizable features of E. willisii are the long, sprawling stems often spread over a large area, sometimes reaching at least 45 cm and often with many crowded nodes, sessile or subsessile leaves with rounded to subcordate bases, and short pedicels, characteristically no longer than the subtending leaves (except sometimes the distal ones where subtending leaves are distinctly reduced in size). It is possible that stem growth in E. willisii is indeterminate versus determinate in E. moschata. Sessile to subsessile leaves occur in E. moschata, especially in the California Sierra Nevada, but petiole length and leaf base shape are variable within populations; lack of petioles and a rounded/subcordate base are fixed characters in E. willisii (as they are also in E. ptilota). Although large colonies of E. moschata are sometimes encountered, the individual plants tend to be erect (in California) and with few distal flowers. In the field, the dense vestiture of E. willisii is a prominent feature, but this is harder to distinguish in pressed specimens, and there is a strong tendency for purple abaxial leaf coloration in E. willisii. Phenology and flower morphology of E. willisii and E. moschata appear to be similar, but E. moschata in north-central California does not occur at as low elevations as E. willisii.
Selected References
None.