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capitate sandmat, head sandmat, head spurge

dwarf broomspurge

Habit Herbs, annual or perennial, with slender to thick and woody rootstock. Herbs, perennial, with woody or fibrous-fleshy, napiform, branched or tuberous taproot, 3–15 mm thick.
Stems

usually ascending (but ranging from decumbent to erect), 15–50 cm, glabrous, strigillose, or pilose.

ascending to erect, densely emerging from woody crown, 5–15 cm, glabrous.

Leaves

opposite;

stipules distinct, filiform or divided into 2–3 subulate-filiform segments, without dark, circular glands at base, 0.6–1.5 mm, pilose;

petioles 0.6–1.3 mm, glabrous, pilose, or strigillose;

blade ovate to narrowly ovate, 4–19 × 2–8 mm, base asymmetric, one side strongly cordate, other side rounded to slightly cordate, margins entire or serrulate (commonly nearly entire with few scattered teeth, often slightly thickened), apex acute, surfaces often with red spot in center, glabrous, pilose, or strigillose; weakly 3-veined from base, usually only midvein conspicuous.

opposite;

stipules connate into lacerate or 2-fid, lanceolate or deltate scale, 0.5–0.9 mm, glabrous;

petiole 0.3–0.9 mm, glabrous;

blade orbiculate-obovate, ovate, or elliptic, 3–6(–8) × 1.8–5 mm, base moderately asymmetric, rounded to truncate, margins entire, apex blunt to acute, surfaces glabrous; 2–3-veined from base but usually only midvein conspicuous.

Involucre

narrowly obconic to narrowly campanulate, 0.8–1.6 × 0.7–1.3 mm, glabrous or pilose;

glands 4, yellow-green to pink or maroon, circular to oblong, 0.2–0.4 × 0.2–0.5 mm;

appendages white to light pink, oblong to reniform or flabellate, 0.2–1.1 × 0.5–1.7 mm, surfaces glabrous, distal margin entire.

broadly campanulate, 1.2–1.5 × 0.8–1.2 mm, glabrous;

glands 4, yellowish to green or purplish, oblong, 0.2–0.4 × 0.5–1 mm;

appendages erect or spreading, white, 0.3–0.6 × 0.8–1.2 mm, usually deeply dissected into 4–5 acuminate lobes, rarely undivided, when divided distal margin rarely entire or crenate.

Staminate flowers

25–40.

12–35.

Pistillate flowers

ovary glabrous or pilose;

styles 0.4–0.6 mm, 2-fid entire length.

ovary glabrous;

styles 0.4–0.5 mm, unbranched thickened-clavate.

Capsules

ovoid to oblate, 1.3–1.9 × 1.4–2.1 mm, glabrous or pilose;

columella 1.1–1.7 mm.

ovoid and broadly triangular, 1.8–2.2(–2.7) × 1.5–2.1 mm, glabrous;

columella 1.5–2.2 mm.

Seeds

pink to pinkish gray, narrowly ovoid to narrowly ovoid-oblong, 4-angled or weakly 3-angled in cross section, 0.9–1.5 × 0.5–0.7 mm, irregularly dimpled, sometimes also with faint transverse ridges that do not pass through abaxial keel.

whitish, oblong, 4-angled in cross section, adaxial faces concave, with long raphe between, 1.5–2(–2.3) × 0.6–0.8 mm, dimpled with faint irregular transverse wrinkles or with up to 10 low, rounded transverse ridges.

Cyathia

in dense, terminal capitate glomerules, with reduced, bractlike leaves subtending cyathia, at tips of main stems and short, leafy, axillary branches;

peduncle 0.1–1.2 mm.

solitary at distal nodes;

peduncle 0.8–1.5 mm.

2n

= 14.

Euphorbia capitellata

Euphorbia jejuna

Phenology Flowering and fruiting year-round in response to sufficient moisture. Flowering and fruiting early spring–summer.
Habitat Gravelly washes, rocky slopes, basaltic talus, disturbed roadsides, primarily desert scrub, desert grasslands, riparian forests, rarely oak-juniper woodlands. Thin calcareous soils (caliche) on limestone hills.
Elevation 600–1600 m. (2000–5200 ft.) 500–900 m. (1600–3000 ft.)
Distribution
from FNA
AZ; NM; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Sinaloa, Sonora)
[WildflowerSearch map]
[BONAP county map]
from FNA
TX; Mexico (Chihuahua, Coahuila)
[BONAP county map]
Discussion

Euphorbia capitellata is a characteristic herb in the Sonoran Desert of southern Arizona, ranging east to extreme southwestern Texas. During peak flowering, plants are attractive due to the dense clusters of cyathia with well-developed involucral gland appendages.

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

Euphorbia jejuna is known in the flora area from only a few collections in Mitchell, Nolan, Terrell, and Val Verde counties. The species is very similar to E. astyla, but differs in its more deeply divided involucral gland appendages and more definitely petiolate, rounder leaves.

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

Source FNA vol. 12, p. 262. FNA vol. 12, p. 274.
Parent taxa Euphorbiaceae > Euphorbia > sect. Anisophyllum 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. 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
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. 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. 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 Chamaesyce capitellata, C. pycnanthema, E. pycnanthema Chamaesyce jejuna
Name authority Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 188. (1859) M. C. Johnston & Warnock: SouthW. Naturalist 5: 97, fig. [p. 98]. (1960)
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