Flora of North America species comparison

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Chylismia sect. Chylismia

Chylismia walkeri

Walker's evening-primrose, Walker's sun-cup
Habit Herbs usually annual, sometimes perennial, rarely biennial.Leaves basal and cauline, usually with well-developed basal rosette; blade usually pinnately or bipinnately lobed, sometimes with scattered, irregular lobes, sometimes lateral lobes greatly reduced or absent, terminal lobe elliptic, narrowly to broadly ovate to oblong, lanceolate, oblanceolate, cordate, or subcordate. 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.
Racemes

erect, elongating after anthesis.
Flowers

usually opening at sunrise, rarely at sunset;

floral tube 0.4–9 mm;

petals usually bright yellow, rarely white or cream, usually with red dots basally, or lavender to purple with white or yellow basally, sometimes with darker flecks near base, fading yellow, orange, reddish, or lavender;

pollen shed singly.

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

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

pedicel 5–30 mm.
Seeds

0.6–1.2 mm.

Chylismia sect. Chylismia

Chylismia walkeri
Distribution
w United States; nw Mexico
sw United States
[WildflowerSearch map]
[BONAP county map]
Discussion

Species 14 (14 in the flora).

Section Chylismia consists of 10 diploid (2n = 14) species, and two that are partly polyploid (2n = 14, 28) [C. scapoidea subsp. scapoidea and C. walkeri subsp. walkeri (only one tetraploid population)]; no chromosome counts are available for the remaining two species, C. atwoodii and C. confertiflora (P. H. Raven 1962, 1969). Species of sect. Chylismia usually occur on sandy desert slopes, flats, and washes, often in sagebrush shrubland in the northern part of its range, or on rock slides or cliffs, mainly in the Mojave and northwestern Sonoran deserts, the Great Basin, and the lower elevations of the surrounding Sierra Nevada and Rocky Mountains. The limits of this range stretch from southeastern Oregon, central and southern Idaho, and central Wyoming, south through Nevada and Utah to eastern and southeastern California, northern Baja California and northwestern Sonora, Mexico, Arizona, northwestern New Mexico, and western Colorado. Several species are rare; C. confertiflora and C. specicola are known only from the Grand Canyon in northwestern Arizona, C. megalantha only from the vicinity of the type locality in Nye County, Nevada, and C. atwoodii also only from a narrow area around its type locality in Kane County, Utah. Others are widespread, especially the very diverse C. claviformis (11 subspp.), C. scapoidea (4 subspp.), C. walkeri (2 subspp.), and C. brevipes (3 subspp.). Chylismia scapoidea is the only species in the genus to occur east of the continental divide, both in Colorado on the upper Arkansas River in Fremont and Pueblo counties, and much more widely in Wyoming. Chylismia does not occur west of the Cascade-Sierra Nevada axis. Because R. A. Levin et al. (2004) included only C. claviformis in their analysis, they did not test the monophyly of sect. Chylismia; however, this section is both geographically distinct and morphologically set apart by the characteristic pinnate leaves (modified in some species, which have retained the entire apical lobe but do not have the smaller lateral lobes). Most species have bright yellow petals with red dots proximally and ultraviolet reflectance distally; some subspecies of C. claviformis have white petals; three species (C. atwoodii, C. heterochroma, and C. megalantha) have lavender or purple petals, often with lavender or purple flecks toward base, and white or yellow at the base and no reflectance, clearly a derived condition within the section (Raven 1962, 1969).

(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. Stamens usually 4, rarely 8, then antipetalous anthers abortive, smaller.
C. exilis
1. Stamens 8, anthers all fertile.
→ 2
2. Petals lavender or purple, often with purple or lavender flecks near base.
→ 3
3. Stigma surrounded by anthers at anthesis, plants autogamous; petals 2–6 mm.
C. heterochroma
3. Stigma exserted beyond anthers at anthesis, plants outcrossing; petals 7–14 mm.
→ 4
4. Capsules 8–14 mm, erect or ascending; floral tubes 4–9 mm.
C. megalantha
4. Capsules 11–25 mm, spreading to reflexed; floral tubes 0.6–1 mm.
C. atwoodii
2. Petals yellow or white, often with red dots at base.
→ 5
5. Capsules distinctly clavate.
→ 6
6. Stigma surrounded by anthers at anthesis; petals 1.5–5.5(–8) mm.
C. scapoidea
6. Stigma exserted beyond anthers at anthesis; petals 2–10 mm.
→ 7
7. Mature capsules sharply reflexed; petals bright yellow.
C. munzii
7. Mature capsules ascending, spreading, erect, or slightly reflexed; petals yellow or white.
→ 8
8. Raceme branches intricate and filiform; leaves in poorly defined basal rosette; capsules 4–10 mm.
C. parryi
8. Raceme branches not filiform; leaves primarily in well-defined basal rosette; capsules 8–40 mm.
→ 9
9. Stamens subequal; leaves usually pinnately lobed, with well-developed lateral lobes, sometimes these reduced or absent, margins dentate, sinuate-dentate, or serrate.
C. claviformis
9. Stamens unequal, differentiated into 2 sets; leaves usually unlobed, rarely pinnately lobed with reduced lateral lobes, margins entire or sparsely denticulate.
C. eastwoodiae
5. Capsules oblong-cylindrical.
→ 10
10. Stigma surrounded by anthers at anthesis; petals 1–6 mm; styles 1.5–6(–7) mm; racemes erect in bud, mature buds individually reflexed.
→ 11
11. Plants perennial, base sometimes woody; leaf blades glabrous or sparsely villous; anthers glabrous.
C. specicola
11. Plants annual or short-lived perennial, base not woody; leaf blades moderately to densely villous; anthers glabrous or sparsely ciliate.
C. walkeri
10. Stigma exserted beyond anthers at anthesis; petals 3–18 mm; styles 7–18 mm; racemes erect or nodding in bud, mature buds individually reflexed or not.
→ 12
12. Racemes erect to nodding, elongating in bud, mature buds individually reflexed; plants virgate; floral tubes 1–3 mm.
C. multijuga
12. Racemes nodding, mostly elongating after flowers open; plants not virgate; floral tubes 3–8 mm.
→ 13
13. Buds without free tips or with subapical free tips 1–2 mm, or with minute apical free tips less than 1 mm, and then bud pubescent but not glandular puberulent; plants branched or unbranched distally; stamens subequal.
C. brevipes
13. Buds with subapical free tips 1–2 mm, glandular puberulent; plants well branched; stamens differentiated into 2 sets.
C. confertiflora
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 Onagraceae > subfam. Onagroideae > tribe Onagreae > Chylismia > sect. Chylismia
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
Subordinate taxa
C. atwoodii, C. brevipes, C. claviformis, C. confertiflora, C. eastwoodiae, C. exilis, C. heterochroma, C. megalantha, C. multijuga, C. munzii, C. parryi, C. scapoidea, C. specicola, C. walkeri
C. walkeri subsp. tortilis, C. walkeri subsp. walkeri
Synonyms Camissonia section tetranthera, Oenothera section tetranthera Camissonia walkeri, Oenothera walkeri
Name authority unknown A. Nelson: Bot. Gaz. 56: 66. (1913) — (as Chylisma)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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