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mountain spurge

Blackfoot sandmat, narrow-leaf spurge

Habit Herbs, perennial, with thick rootstock. Herbs, perennial, with moderately to strongly thickened rootstock.
Stems

erect, branched, 40–90 cm, glabrous.

erect, 12–43 cm, uniformly strigose.

Leaves

petiole 0.5–1 mm;

blade elliptic to oblong, 8–20(–40) × 3–6 mm, base truncate, rounded, or attenuate, margins entire, apex obtuse or acute, sometimes slightly mucronate, surfaces glabrous;

venation inconspicuous, only midvein prominent.

opposite;

stipules distinct, linear-subulate or nodiform to papilliform nodiform to papilliform stipules often reddish brown, 0.1–0.7 mm, strigose;

petiole 0.3–1.2 mm, strigose;

blade: proximal ovate to ovate-elliptic, distal linear to elliptic-linear, 7–41 × 2–5 mm, distal leaf blades more than 6 times as long as wide, base asymmetric, cuneate to rounded, margins entire, often involute on drying, apex acute, surfaces usually short strigose, occasionally glabrous adaxially;

venation pinnate, only midvein conspicuous.

Involucre

turbinate or campanulate, 1.5–2.5 × 1.1–1.9 mm, glabrous;

glands 4, crescent-shaped to semicircular, 0.5–0.8 × 1–1.8 mm;

horns usually convergent, 0.2–0.8 mm.

turbinate to campanulate-turbinate, 1–1.5 × 1–1.4 mm, strigose;

glands 4, green to yellow-green, concave, narrowly oblong, 0.2–0.4 × 0.4–0.7 mm;

appendages white, flabellate, 0.5–1.1 × 0.3–0.5 mm, distal margin shallowly and irregularly toothed.

Staminate flowers

8–12.

16–26.

Pistillate flowers

ovary glabrous;

styles 1–1.8 mm, 2-fid.

ovary strigose;

styles 0.3–0.5 mm, 2-fid at apex to almost 1/2 length.

Capsules

depressed-ovoid, 4.3–5 × 5–6 mm, 3-lobed;

cocci rounded, smooth, glabrous;

columella 3.5–4 mm.

broadly ovoid, 2–2.6 × 2.5–3 mm, strigose;

columella 1.6–2.2 mm.

Seeds

gray to dark brown, ovoid-oblong, truncate at both ends, 2.6–3.4 × 2–2.6 mm, shallowly pitted to almost smooth;

caruncle conic, 1 × 0.8 mm.

white, ovoid, 4-angled in cross section, 1.7–2.2 × 1.1–1.2 mm, transversely low-ridged or wrinkled.

Cyathial

arrangement: terminal pleiochasial branches 3–5(–6), each 3–4 times 2-branched;

pleiochasial bracts ovate-lanceolate to slightly subpandurate, similar in size or wider than distal leaves;

dichasial bracts distinct, lanceolate to broadly ovate, base usually truncate to rounded or subcordate, sometimes attenuate, margins entire or slightly crenulate, apex usually obtuse to acute, occasionally acuminate;

axillary cymose branches 2–8.

Cyathia

peduncle 1–3 mm.

solitary at distal nodes;

peduncle 1.1–2.4 mm.

2n

= 26.

= 28.

Euphorbia chamaesula

Euphorbia angusta

Phenology Flowering and fruiting spring–summer. Flowering and fruiting early spring–fall.
Habitat Clearings in ponderosa pine forests, montane roadsides, dry streambeds, creek banks, sandy and gravelly soils. Rocky limestone soils.
Elevation 1700–2700 m. (5600–8900 ft.) 400–1200 m. (1300–3900 ft.)
Distribution
from FNA
AZ; NM; Mexico (Chihuahua, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico (Coahuila)
[BONAP county map]
Discussion

Euphorbia chamaesula is easily distinguished from other perennial members of subg. Esula in western North America by its larger capsules and the vegetative shoots (without cyathia) that arise from the distal nodes of the stem proximal to the pleiochasia.

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

Euphorbia angusta, which in the flora area is known from the trans-Pecos region to the Edwards Plateau, is easily recognized by its erect habit, linear leaves, and relatively showy involucral gland appendages with toothed margins. The species is closely related to E. acuta and the Mexican endemic E. johnstonii Mayfield (M. H. Mayfield 1991); it is not only morphologically distinctive but is also the only species in sect. Anisophyllum with C3 photosynthesis (R. F. Sage et al. 2011; T. L. Sage et al. 2011; G. L. Webster 1975).

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

Source FNA vol. 12, p. 300. FNA vol. 12, p. 260.
Parent taxa Euphorbiaceae > Euphorbia > subg. Esula Euphorbiaceae > Euphorbia > sect. Anisophyllum
Sibling taxa
E. aaron-rossii, E. abramsiana, E. acuta, E. agraria, E. albomarginata, E. alta, E. angusta, E. antisyphilitica, E. arizonica, E. astyla, E. austrotexana, E. bicolor, E. bifurcata, E. bilobata, E. blodgettii, E. bombensis, E. brachycera, E. capitellata, E. carunculata, E. chaetocalyx, E. cinerascens, E. commutata, E. conferta, E. cordifolia, E. corollata, E. crenulata, E. cumulicola, E. cuphosperma, E. curtisii, E. cyathophora, E. cyparissias, E. davidii, E. deltoidea, E. dendroides, E. dentata, E. discoidalis, E. eriantha, E. exigua, E. exserta, E. exstipulata, E. falcata, E. fendleri, E. florida, E. floridana, E. garberi, E. georgiana, E. geyeri, E. glyptosperma, E. golondrina, E. gracillima, E. graminea, E. helioscopia, E. helleri, E. heterophylla, E. hexagona, E. hirta, E. hooveri, E. humistrata, E. hypericifolia, E. hyssopifolia, E. indivisa, E. innocua, E. inundata, E. ipecacuanhae, E. jaegeri, E. jejuna, E. laredana, E. lasiocarpa, E. lata, E. lathyris, E. longicruris, E. lurida, E. macropus, E. maculata, E. marginata, E. meganaesos, E. melanadenia, E. mendezii, E. mercurialina, E. mesembrianthemifolia, E. micromera, E. misera, E. missurica, E. myrsinites, E. nephradenia, E. nutans, E. oblongata, E. ocellata, E. ophthalmica, E. ouachitana, E. parishii, E. parryi, E. pediculifera, E. peplidion, E. peplus, E. perennans, E. pergamena, E. pinetorum, E. platyphyllos, E. platysperma, E. polycarpa, E. polygonifolia, E. polyphylla, E. porteriana, E. prostrata, E. pubentissima, E. purpurea, E. radians, E. rayturneri, E. revoluta, E. roemeriana, E. rosescens, E. schizoloba, E. serpens, E. serpillifolia, E. serrata, E. serrula, E. setiloba, E. simulans, E. spathulata, E. stictospora, E. strictior, E. telephioides, E. terracina, E. tetrapora, E. texana, E. theriaca, E. thymifolia, E. tithymaloides, E. trachysperma, E. trichotoma, E. vallis-mortae, E. velleriflora, E. vermiculata, E. villifera, E. virgata, E. wrightii, E. yaquiana
E. aaron-rossii, E. abramsiana, E. acuta, E. agraria, E. albomarginata, E. alta, E. antisyphilitica, E. arizonica, E. astyla, E. austrotexana, E. bicolor, E. bifurcata, E. bilobata, E. blodgettii, E. bombensis, E. brachycera, E. capitellata, E. carunculata, E. chaetocalyx, E. chamaesula, E. cinerascens, E. commutata, E. conferta, E. cordifolia, E. corollata, E. crenulata, E. cumulicola, E. cuphosperma, E. curtisii, E. cyathophora, E. cyparissias, E. davidii, E. deltoidea, E. dendroides, E. dentata, E. discoidalis, E. eriantha, E. exigua, E. exserta, E. exstipulata, E. falcata, E. fendleri, E. florida, E. floridana, E. garberi, E. georgiana, E. geyeri, E. glyptosperma, E. golondrina, E. gracillima, E. graminea, E. helioscopia, E. helleri, E. heterophylla, E. hexagona, E. hirta, E. hooveri, E. humistrata, E. hypericifolia, E. hyssopifolia, E. indivisa, E. innocua, E. inundata, E. ipecacuanhae, E. jaegeri, E. jejuna, E. laredana, E. lasiocarpa, E. lata, E. lathyris, E. longicruris, E. lurida, E. macropus, E. maculata, E. marginata, E. meganaesos, E. melanadenia, E. mendezii, E. mercurialina, E. mesembrianthemifolia, E. micromera, E. misera, E. missurica, E. myrsinites, E. nephradenia, E. nutans, E. oblongata, E. ocellata, E. ophthalmica, E. ouachitana, E. parishii, E. parryi, E. pediculifera, E. peplidion, E. peplus, E. perennans, E. pergamena, E. pinetorum, E. platyphyllos, E. platysperma, E. polycarpa, E. polygonifolia, E. polyphylla, E. porteriana, E. prostrata, E. pubentissima, E. purpurea, E. radians, E. rayturneri, E. revoluta, E. roemeriana, E. rosescens, E. schizoloba, E. serpens, E. serpillifolia, E. serrata, E. serrula, E. setiloba, E. simulans, E. spathulata, E. stictospora, E. strictior, E. telephioides, E. terracina, E. tetrapora, E. texana, E. theriaca, E. thymifolia, E. tithymaloides, E. trachysperma, E. trichotoma, E. vallis-mortae, E. velleriflora, E. vermiculata, E. villifera, E. virgata, E. wrightii, E. yaquiana
Synonyms Tithymalus chamaesula Chamaesyce angusta
Name authority Boissier: Cent. Euphorb., 38. (1860) Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 189. (1859)
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