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summer spurge

Habit Herbs, perennial, with spreading rootstock. Herbs, annual, with taproot.
Stems

erect or ascending, unbranched, solitary or few, previous year's dead stems not persistent, 45–70 cm, usually densely puberulent to sericeous, rarely glabrous.

erect, usually branched near base, 6–22 cm, glabrous.

Leaves

alternate;

stipules to 0.1 mm;

petiole (0–)1–2 mm (or absent), densely puberulent;

blade usually linear, rarely ovate, 25–55 × 1.5–4 mm, base cuneate, margins entire, revolute, apex rounded, abaxial surface glabrous or puberulent to sericeous, adaxial surface glabrous;

venation often obscure on smaller leaves, midvein conspicuous.

petiole absent;

blade linear to slightly lanceolate or linear-oblanceolate, 5–18 × 0.5–2.5 mm, base linear attenuate, margins entire, apex rounded to obtuse or acute, surfaces glabrous;

venation pinnate, midvein prominent.

Involucre

campanulate, 1.2–1.4 × 1.2–2 mm, sparsely to densely puberulent;

glands 5, green, reniform, 0.2–0.3 × 0.5–0.6 mm;

appendages white, orbiculate to oblong, (0.5–)1–1.7 × 1–1.5 mm, entire.

infundibular, 0.8–1.1 × 0.6–0.9 mm, glabrous;

glands 4, crescent-shaped; 0.2–0.4 × 0.5–0.6 mm;

horns divergent, 0.5–0.7 mm.

Staminate flowers

20–25.

5–10.

Pistillate flowers

ovary glabrous or sparsely strigose;

styles 0.5–1.1 mm, 2-fid at apex to 1/2 length.

ovary glabrous;

styles 0.3–0.5 mm, 2-fid.

Capsules

globose, 1.8–3 × 2.5–4.8 mm, glabrous or sparsely strigose;

columella 2.3–2.5 mm.

ovoid-globose, 1.8–2.2 × 3–3.2 mm, slightly 3-lobed;

cocci rounded, smooth, glabrous;

columella 1.5–2 mm.

Seeds

light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions;

caruncle absent.

white to gray, ellipsoid, 1.4–1.7 × 1–1.3 mm, with deep, irregular to rounded, shallow to concave depressions over entire surface;

caruncle reniform-ovate, depressed-conic, 0.5–0.7 × 0.7–1 mm.

Cyathia

in terminal pleiochasia;

peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous.

peduncle 0–0.5 mm.

Cyathial

arrangement: terminal pleiochasial branches 3, 1–3 times 2-branched;

pleiochasial bracts similar in shape to but slightly shorter and wider than distal leaves;

dichasial bracts distinct, not imbricate, reniform-ovate to subdeltate-ovate or broadly ovate-lanceolate, base obliquely truncate to rounded, margins entire, apex obtuse to broadly acuminate;

axillary cymose branches 0–3.

Euphorbia discoidalis

Euphorbia austrotexana

Phenology Flowering and fruiting late spring–fall.
Habitat Sand hills, pine savannas, woodland borders, open fields with sandy soils.
Elevation 0–150 m. (0–500 ft.)
Distribution
from FNA
AL; FL; GA; LA; MS; TX
[WildflowerSearch map]
[BONAP county map]
from FNA
TX
Discussion

M. J. Huft (1979) remarked that Euphorbia discoidalis is uncommon west of Alabama and referred many narrow-leaved specimens from Louisiana and Texas to E. corollata. K. R. Park (1998) included them in an expanded E. discoidalis, and that is followed here. The western populations can be distinguished from E. corollata by their shorter involucral gland appendages and revolute leaf margins. Further study of these western populations is warranted.

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

Varieties 2 (2 in the flora).

Euphorbia austrotexana occurs in stabilized sandy soil in the south Texas plains (M. H. Mayfield 2013). It is similar to E. longicruris but differs from that species in its often narrowly oblanceolate to linear leaves and its white to gray, ellipsoid seeds that are covered with minute, concave depressions.

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

Key
1. Stems 10–22 cm; leaf blades linear-oblanceolate, apices rounded; dichasial bracts reniform-ovate to subdeltate-ovate, bases truncate; seeds 1.6–1.7 × 1.1–1.3 mm, surfaces with regular concave depressions; Atascosa, Bexar, Wilson counties.
var. austrotexana
1. Stems 6–13 cm; leaf blades linear to slightly lanceolate, apices acute; dichasial bracts broadly ovate-lanceolate, bases rounded; seeds 1.4–1.5 × 1–1.1 mm, surfaces with irregular, not obviously concave depressions; Jim Hogg, Kenedy counties.
var. carrii
Source FNA vol. 12, p. 245. FNA vol. 12, p. 298.
Parent taxa Euphorbiaceae > Euphorbia > sect. Alectoroctonum Euphorbiaceae > Euphorbia > subg. Esula
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. 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. 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. 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
Subordinate taxa
E. austrotexana var. austrotexana, E. austrotexana var. carrii
Synonyms Tithymalopsis discoidalis
Name authority Chapman: Fl. South. U.S., 401. (1860) Mayfield: J. Bot. Res. Inst. Texas 7: 634, figs. 1, 2[row 3, left & center]. (2013)
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