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Walker's evening-primrose, Walker's sun-cup

Photo is of parent taxon
Habit Herbs annual or short-lived perennial, villous, usually densely so proximally, less dense to glabrate distally, sometimes hairs somewhat appressed and shorter on leaves, also sometimes glandular puberulent on distal parts.
Stems

slender, unbranched or branched from base, 10–60 cm.

Leaves

in basal rosette and/or cauline, often purple-dotted, 2–22 × 0.4–3.5 cm;

petiole 0.4–8 cm;

blade pinnately lobed, sometimes lateral lobes greatly reduced or absent and blade reduced to terminal lobe only, terminal lobe oblong or cordate to ovate, 1–5 × 0.5–3.2 cm, margins serrate, brown oil cells prominently lining veins abaxially.

primarily cauline, rarely forming basal rosette;

blade with only terminal lobe well developed, sometimes pinnately lobed, lateral lobes usually greatly reduced or absent.

Racemes

erect, elongating after anthesis.

Flowers

opening at sunrise;

buds individually reflexed, with apical free tips less than 1 mm;

floral tube 0.5–1.5 mm, glabrous or sparsely villous inside;

sepals 1.5–5 mm;

petals bright yellow, fading pale orange or lavender, 1–6 mm;

stamens unequal, filaments of antisepalous stamens 1–3 mm, those of antipetalous ones 0.3–2 mm, anthers 0.5–2 mm, glabrous or sparsely ciliate;

style 1.5–6 mm, stigma surrounded by anthers at anthesis.

floral tube 0.5–1.3 mm;

sepals 1.5–2 mm;

petals 1–3 mm;

anthers 0.5–0.8 mm, glabrous;

style 1.5–4 mm.

Capsules

spreading or ascending, oblong-cylindrical, 11–45 mm;

pedicel 5–30 mm.

pedicel 5–15 mm.

Seeds

0.6–1.2 mm.

2n

= 14, 28.

Chylismia walkeri

Chylismia walkeri subsp. walkeri

Phenology Flowering Apr–Jun.
Habitat Loose slides of limestone and other sedimentaries, sandy washes.
Elevation 900–1800 m. (3000–5900 ft.)
Distribution
sw United States
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CO; NM; UT
[BONAP county map]
Discussion

Subspecies 2 (2 in the flora).

P. H. Raven (1962, 1969) determined this species to be self-incompatible and primarily autogamous.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Subspecies walkeri is nearly confined to the Colorado Plateau, known from Mesa County, Colorado, and Emery County, Utah, south to Montezuma County, Colorado, San Juan County, New Mexico, and central Coconino and northeastern Mohave counties, Arizona.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Leaves primarily cauline, rarely forming inconspicuous basal rosette, lateral lobes usually greatly reduced or absent; petals 1–3 mm; anthers 0.5–0.8 mm.
subsp. walkeri
1. Leaves primarily basal, forming conspicuous rosette, cauline reduced or absent, lateral lobes usually well developed; petals 2.8–6 mm; anthers 1–2 mm.
subsp. tortilis
Source FNA vol. 10. FNA vol. 10.
Parent taxa Onagraceae > subfam. Onagroideae > tribe Onagreae > Chylismia > sect. Chylismia Onagraceae > subfam. Onagroideae > tribe Onagreae > Chylismia > sect. Chylismia > Chylismia walkeri
Sibling taxa
C. arenaria, C. atwoodii, C. brevipes, C. cardiophylla, C. claviformis, C. confertiflora, C. eastwoodiae, C. exilis, C. heterochroma, C. megalantha, C. multijuga, C. munzii, C. parryi, C. scapoidea, C. specicola
C. walkeri subsp. tortilis
Subordinate taxa
C. walkeri subsp. tortilis, C. walkeri subsp. walkeri
Synonyms Camissonia walkeri, Oenothera walkeri Camissonia bolanderin., C. dominguezescalanteorum, Oenothera multijuga var. orientalis
Name authority A. Nelson: Bot. Gaz. 56: 66. (1913) — (as Chylisma) unknown
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