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riverside spineflower, Xantus' spineflower

prostrate spineflower

Habit Plants erect to infrequently spreading, (0.3–)0.5–2.5(–3) × 0.5–3(–5) dm, thinly pubescent. Plants prostrate to decumbent, 0.2–0.8 × 0.5–4(–5) dm, thinly pubescent.
Leaves

basal or nearly so;

petiole 1–2(–3) cm;

blade oblong or oblong-ovate to ovate, 0.3–1(–1.5) × 0.3–0.8(–1) cm, thinly pubescent adaxially, densely tomentose abaxially.

basal;

petiole 0.5–2(–3) cm;

blade oblanceolate, (0.5–)1–3(–4) × 0.1–0.7(–1.2) cm, thinly pubescent.

Inflorescences

mostly flat-topped and openly branched, usually reddish;

bracts persistent, 2, usually leaflike at proximal nodes and similar to proximal leaf blades only more reduced, short-petiolate, oblong-ovate to ovate, 0.3–0.8 cm × 2–6 mm, becoming sessile, reduced and scalelike at distal nodes, linear, acicular, often acerose, 0.1–0.4 cm × 0.5–1 mm, awns straight, 0.5–1 mm.

with involucres in small, open clusters 0.3–1 cm diam., greenish yellow to green or reddish green;

bracts 2, sessile, leaflike and similar to proximal leaf blades only reduced, linear-oblanceolate to elliptic, 0.3–1(–1.5) cm × 1.5–5(–8) mm, rapidly reduced and scalelike at distal nodes, linear, acicular, often acerose, 0.1–0.5 cm × (0.3–)0.5–3 mm, awns straight, 0.2–1 mm.

Involucres

in open clusters with 1 at node of dichotomies, reddish, cylindric, not ventricose, 3–4.5 mm, not corrugate, without scarious or membranous margins, thinly to densely pubescent;

teeth spreading, unequal, 0.7–1.5 mm, 3 longer ones more erect than 3 shorter and less-prominent ones;

awns uncinate, 0.5–1 mm.

3–10, rarely more, greenish yellow to reddish green, cylindric or narrowly to broadly campanulate, not ventricose,1.5–3 mm, faintly corrugate, without scarious or membranous margins, thinly pubescent with spreading hairs, longest hairs on ribs and at base;

teeth spreading, equal, 1–2.5 mm, or divergent, thickened basally, unequal, 1–2 mm or 2.5–5 mm with hyaline margins between teeth;

awns uncinate, 0.2–0.5 mm.

Flowers

long-exserted;

perianth rose to red, infrequently with white lobes, cylindric, 4.5–6 mm, pubescent;

tepals connate ca. 2/3 their length, monomorphic to slightly dimorphic, narrowly oblanceolate, rounded apically, those of outer whorl occasionally slightly broader and longer than those of inner whorl;

stamens 9, mostly included;

filaments distinct, 4–6 mm, glabrous;

anthers pink to red, oblong, 0.5–0.6 mm.

exserted;

perianth yellow or sometimes white, cylindric, (1.7–)2–3 mm, pubescent;

tepals connate ca. 2/3 their length, essentially monomorphic, narrowly oblong to narrowly obovate, occasionally with outer lobes slightly broader and longer than inner ones, entire apically;

stamens 9, exserted;

filaments connate basally into 0.2–1 mm tube, (0.3–)0.5–2.5 mm, pilose-ciliate;

anthers cream to pale yellow, oblong, (0.2–)0.5–0.7 mm.

Achenes

brown, lenticular, 4–4.5 mm.

brown, lenticular, 1.5–2.5 mm.

2n

= (38), 40, (42, 44, 46).

Chorizanthe xanti

Chorizanthe procumbens

Phenology Flowering Apr–Jun.
Habitat Sandy to gravelly flats and slopes, coastal grassland, coastal sage, chaparral, and desert scrub communities
Elevation (0-)10-1300 m ((0-)0-4300 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

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

Chorizanthe procumbens is a variable complex of widely scattered, locally infrequent to common populations that occur from the Santa Monica, San Gabriel, and San Bernardino mountains southward through western Riverside and Orange counties to San Diego County. In a strict sense, prostrate plants from San Diego southward belong to C. procumbens (including C. jonesiana) while decumbent plants to the north are C. uncinata (C. procumbens sensu G. J. Goodman 1934), if such a distinction is considered taxonomically useful. Plants with a grayish hue south of our range in Baja California have been described as C. chaetophora. All of our plants have a greenish yellow cast.

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

Key
1. Involucres thinly pubescent
var. xanti
1. Involucres densely white-pubescent
var. leucotheca
Source FNA vol. 5, p. 463. FNA vol. 5, p. 462.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala
Sibling taxa
C. angustifolia, C. biloba, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, C. diffusa, C. douglasii, C. fimbriata, C. howellii, C. leptotheca, C. membranacea, C. obovata, C. orcuttiana, C. palmeri, C. parryi, C. polygonoides, C. procumbens, C. pungens, C. rectispina, C. rigida, C. robusta, C. spinosa, C. staticoides, C. stellulata, C. uniaristata, C. valida, C. ventricosa, C. watsonii, C. wheeleri
C. angustifolia, C. biloba, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, C. diffusa, C. douglasii, C. fimbriata, C. howellii, C. leptotheca, C. membranacea, C. obovata, C. orcuttiana, C. palmeri, C. parryi, C. polygonoides, C. pungens, C. rectispina, C. rigida, C. robusta, C. spinosa, C. staticoides, C. stellulata, C. uniaristata, C. valida, C. ventricosa, C. watsonii, C. wheeleri, C. xanti
Subordinate taxa
C. xanti var. leucotheca, C. xanti var. xanti
Synonyms C. chaetophora, C. jonesiana, C. procumbens var. albiflora, C. procumbens var. mexicana, C. uncinata
Name authority S. Watson: Proc. Amer. Acad. Arts 12: 272. (1877) Nuttall: Proc. Acad. Nat. Sci. Philadelphia 4: 17. (1848)
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