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diffuse spineflower

Orcutt spineflower, Orcutt's spineflower, San Diego spineflower

Habit Plants spreading, decumbent, prostrate, or rarely slightly erect, 0.3–1(–1.5) × 0.5–2(–10) dm, villous. Plants prostrate, 0.1–0.5 × 0.3–2(–2.5) dm, villous.
Leaves

basal;

petiole 0.2–1.8(–2) cm;

blade oblanceolate, 0.3–2 × 0.1–0.4 cm, villous.

basal;

petiole 1–2 cm;

blade narrowly oblanceolate, 0.5–1.5 × 0.2–0.35(–0.5) cm, thinly pubescent.

Inflorescences

rather dense with secondary branches suppressed, white to greenish;

bracts 2, similar to leaf blades at proximal nodes only reduced, short-petiolate, becoming linear and aciculate at distal nodes, acerose, 0.3–2 cm × 1–4 mm, awns absent.

with involucres in small clusters 0.5–1 cm diam., greenish;

bracts 2, sessile, unequal, 1 laminar and oblanceolate, 0.3–1 cm × 1–3 mm, awnless, this opposite linear, acicular, greatly reduced, 0.1–0.2 cm × 0.3–0.6 mm bract terminated by short, straight awn 0.6–1 mm.

Involucres

1, mostly greenish, cylindric, not ventricose, 2–2.5 mm, with thin to broad and then conspicuous white or pinkish to purple, scarious margins extending nearly full length of awn, not corrugate, villous-hirsute;

teeth spreading to divergent, equal, 0.5–1 mm, awns uncinate with longer ones 1–2 mm, anterior one mostly 2 mm, alternating with shorter (0.5–1 mm) ones.

1, greenish, campanulate, 3-ribbed, 0.8–2 mm, faintly corrugate, pubescent;

teeth 3, equal, 1.8–2 mm;

awns uncinate, 0.6–1 mm.

Flowers

exserted;

perianth bicolored with floral tube lemon-yellow and tepals white, campanulate, 2.5–3 mm, glabrous;

tepals connate ca. 1/3 their length, monomorphic, oblong, acute to obtuse and entire apically;

stamens 3–9, slightly exserted;

filaments distinct, 1.5–2 mm, glabrous;

anthers yellow, oval, 0.3–0.4 mm.

1, included to slightly exserted;

perianth yellow, cylindric, 1.5–1.8 mm, densely pubescent abaxially;

tepals connate ca. 1/2 their length, monomorphic, narrowly oblanceolate, obtuse to truncate, entire apically, slightly spreading;

stamens 9, slightly exserted;

filaments distinct, 0.5–0.8 mm, glabrous;

anthers reddish, ovate, 0.2–0.3 mm.

Achenes

dark brown, globose-lenticular, 2–2.5 mm.

dark brown, lenticular, 2–2.2 mm.

2n

= 38, 40, 42.

= (76, 78), 80, (84).

Chorizanthe diffusa

Chorizanthe orcuttiana

Phenology Flowering Apr–Jul. Flowering Mar–May.
Habitat Sandy to gravelly flats and slopes, coastal scrub communities, pine-oak woodlands Sandy soil, mesas and hills near coast, coastal scrub communities
Elevation 30-800 m (100-2600 ft) 60-200 m (200-700 ft)
Distribution
from FNA
CA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
[BONAP county map]
Discussion

The involucral margins of Chorizanthe diffusa vary greatly. In some individuals, the white margins are barely visible. Plants with the margins of the involucre are predominantly white have been designated var. nivea. A full gradation between the extremes may be observed in most populations, although in coastal sands var. nivea is often the dominant expression. Diffuse spineflower occurs near the coast and in the Coast Ranges of central California.

Chorizanthe diffusa has been shown to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary-organ culture model. This inhibitory activity is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis (see H. S. Chung et al. 1999).

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

Of conservation concern.

Chorizanthe orcuttiana is known from a few populations on coastal mesas and hills near San Diego, San Diego County. It is federally listed as endangered. The species is an octoploid that may well have resulted from an ancient hybridization and doubling of chromosomes involving C. procumbens and C. polygonoides var. longispina. The Orcutt spineflower grows in soft, white sand; C. procumbens and C. polygonoides var. longispina are restricted to gravelly sites.

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

Source FNA vol. 5, p. 452. FNA vol. 5, p. 467.
Parent taxa Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Ptelosepala Polygonaceae > subfam. Eriogonoideae > Chorizanthe > subg. Amphietes > sect. Acanthogonum
Sibling taxa
C. angustifolia, C. biloba, C. blakleyi, C. brevicornu, C. breweri, C. clevelandii, C. corrugata, C. cuspidata, 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. xanti
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. 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. xanti
Synonyms C. andersonii, C. diffusa var. nivea, C. nivea, C. pungens var. diffusa, C. pungens var. nivea
Name authority Bentham: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 26. (1856) Parry: Proc. Davenport Acad. Nat. Sci. 4: 54. (1884)
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