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riverside spineflower, Xantus' spineflower

Habit Plants erect to infrequently spreading, (0.3–)0.5–2.5(–3) × 0.5–3(–5) dm, thinly pubescent. Plants prostrate to spreading or erect, mostly thinly pubescent.
Stems

sometimes disarticulating at each node.

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.

blades linear to lanceolate, obovate, round, or spatulate.

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.

bracts mostly 2, opposite, scalelike or if leaflike then similar to basal leaves only reduced, occasionally deciduous in early anthesis, with or without awns.

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.

cylindric to narrowly turbinate, campanulate, or urceolate, occasionally ventricose basally, 3-,5-, or 6-toothed, with or without membranous or scarious margins;

teeth erect to spreading or divergent, connate at least 1/2 their length, typically shallow, mostly unequal, with alternating long and short awns, often with anterior one longest.

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.

1(–2), white to pink or rose, maroon or purple, or yellow, thinly pubescent at least along midribs abaxially;

stamens 3–9;

filaments adnate at base of floral tube or faucially;

filaments sometimes connate into short tube.

Achenes

brown, lenticular, 4–4.5 mm.

brown, lenticular or globose-lenticular, or 3-gonous.

Seeds

embryo straight or rarely curved.

Chorizanthe xanti

Chorizanthe subg. Amphietes

Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
w United States; nw Mexico; sw South America
Discussion

Varieties 2 (2 in the flora).

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

Species 39 (31 in the flora).

Most species of subg. Amphietes are found in California. Of the others, one is known only from southernmost Peru to central Chile (Chorizanthe commissuralis J. Rémy), while the rest are known only from Baja California, Mexico. Those include C. inequalis S. Stokes, C. turbinata Wiggins, C. mutabilis Brandegee, C. rosulenta Reveal, C. pulchella Brandegee, C. flava Brandegee, and C. interposita Goodman. The latter is the only member of sect. Clastoscapa, the only section of subg. Amphietes not found in our flora.

(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. 450.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala Polygonaceae > subfam. Eriogonoideae > Chorizanthe
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
Subordinate taxa
C. xanti var. leucotheca, C. xanti var. xanti
Name authority S. Watson: Proc. Amer. Acad. Arts 12: 272. (1877) Reveal & Hardham: Phytologia 66: 113. (1989)
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