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

Habit Herbs annual, densely villous and strigillose, glandular puberulent on distal parts. 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

well branched, 15–50 cm.

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

Leaves

in well-developed basal rosette and also cauline, 7–20 × 1.5–2.5 cm;

petiole 1–4(–8) cm;

blade pinnately lobed, terminal lobe oblanceolate to narrowly ovate, 2.5–5 × 1–2.5 cm, margins irregularly dentate, oil cells on abaxial surface inconspicuous.

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.

Racemes

nodding, dense, mostly elongating after flowers open.

erect, elongating after anthesis.

Flowers

opening at sunrise;

buds with conspicuous, subapical free tips 1–2 mm;

floral tube 3–5 mm, short-villous inside proximally;

sepals 9–12 mm;

petals bright yellow, with red dots at base, fading lavender, 12–18 mm;

stamens unequal, filaments of antisepalous stamens 6–8 mm, those of antipetalous ones 4–5 mm, anthers 4–6 mm, ciliate;

style 11–18 mm, stigma exserted beyond anthers at anthesis.

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.

Capsules

ascending or spreading, oblong-cylindrical, immature capsule to 35 mm;

pedicel 5–15 mm.

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

pedicel 5–30 mm.

Seeds

not known.

0.6–1.2 mm.

Chylismia confertiflora

Chylismia walkeri

Phenology Flowering Apr–May.
Habitat Cinder soil.
Elevation 1300–1400 m. (4300–4600 ft.)
Distribution
from FNA
AZ
[BONAP county map]
sw United States
[WildflowerSearch map]
[BONAP county map]
Discussion

Chylismia confertiflora is known only from the type locality on the east side and base of Vulcan’s Throne, Toroweap Valley, Grand Canyon National Monument in Mohave County. P. H. Raven (1962, 1969) assumed this species to be self-incompatible, based on the large flowers with the stigma elevated above the anthers.

A. Cronquist et al. (1997c) treated Chylismia confertiflora as part of C. brevipes, with a comment about the capsule dimensions, and indicated they consider the differences to be one end of the spectrum of a variation within C. brevipes. Although known from very few collections and sparse field data, P. H. Raven (1962, 1969) considered it to be distinct and to be most closely related to C. brevipes and to C. multijuga. He distinguished it from the latter by its larger flowers, nodding inflorescences, and large buds; and from the former by its glandular puberulent sepals, unequal stamens, and uniformly branched habit. In addition, the very restricted range of C. confertiflora is outside (to the east) of the range of C. brevipes. Chylismia multijuga grows within a few miles of the only know locality, but in this area C. confertiflora is very distinct from that species. Further collections and more detailed study of the overall morphological patterns as well as, perhaps, molecular data may clarify whether this is best considered to be an extremely restricted distinct species or a somewhat distinct outlier of the variable C. brevipes.

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

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.)

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
Sibling taxa
C. arenaria, C. atwoodii, C. brevipes, C. cardiophylla, C. claviformis, C. eastwoodiae, C. exilis, C. heterochroma, C. megalantha, C. multijuga, C. munzii, C. parryi, C. scapoidea, C. specicola, C. walkeri
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
Subordinate taxa
C. walkeri subsp. tortilis, C. walkeri subsp. walkeri
Synonyms Oenothera confertiflorap., Camissonia confertiflora Camissonia walkeri, Oenothera walkeri
Name authority (P. H. Raven) W. L. Wagner & Hoch: Syst. Bot. Monogr. 83: 207. (2007) A. Nelson: Bot. Gaz. 56: 66. (1913) — (as Chylisma)
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