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Hill country silverbush

Yuma or New Mexico silverbush, Yuma silverbush

Habit Herbs, perennial, monoecious or dioecious, to 5 dm. Herbs, annual or perennial, monoecious, to 5 dm.
Stems

erect to ascending, hairy, hairs malpighiaceous.

erect or prostrate, usually densely to sparsely hairy, rarely glabrous, hairs malpighiaceous.

Leaves

stipules deciduous, linear-lanceolate, to 1 mm, margins not glandular;

petiole absent;

blade elliptic, 1.5–4 × 0.6–2 cm, margins entire, without glands, surfaces hairy, hairs malpighiaceous.

stipules deciduous, ovate, lanceolate to subulate, 0.5–2.3 mm, margins not glandular;

petiole 1–10 mm;

blade elliptic to ovate, obovate, or narrowly lanceolate, 1–10.5 × 0.2–3 cm, margins serrate, serrulate, or entire, without glands, surfaces usually densely to sparsely hairy, rarely glabrous, hairs malpighiaceous.

Inflorescences

unisexual, 3–8 cm;

bracts linear-lanceolate, 2–4.5 mm, margins without glands.

bisexual, 0.4–1.5 cm;

bracts ovate to elliptic, 0.8–2 mm, margins without glands.

Flowers

without pink dye when wetted.

without pink dye when wetted.

Staminate flowers

sepals lanceolate to narrowly elliptic, 4–5.5 × 1.1–1.4 mm;

petals cuneate-elliptic to cuneate-obovate, 3.3–4 × 1.6–3 mm, free from androphore;

nectary glands oblong, 0.4–0.5 × 0.3–0.4 mm, adnate to androphore, glabrous;

stamens 10, staminodes 0.

sepals lanceolate, 0.9–2.5 × 0.4–1.4 mm;

petals elliptic to obovate, 1.5–3.5 × 0.6–2 mm, free from androphore;

nectary glands elliptic to oblate, 0.3–0.5 × 0.1–0.2 mm, free from androphore, glabrous;

stamens 10, staminodes 0 or 3–5, glabrous.

Pistillate flowers

sepals lanceolate to elliptic, 6–7 × 1.7–3.2 mm, without glands;

petals 0 or 5, linear, 0–1.7 mm;

nectary glands oblong, 0.5 × 0.7 mm, glabrous;

ovary tomentose to lanulose;

styles 1.5–3 mm, tomentose;

stigmas flattened.

sepals lanceolate to elliptic, 2.3–6.5 × 0.6–1.6 mm, without glands;

petals 5, elliptic, 0.7–3 × 0.4–1.6 mm;

nectary glands elliptic, 0.4–0.6 × 0.3–0.4 mm, glabrous;

ovary sericeous, strigose, or hispidulous;

styles 1–1.8 mm, glabrous;

stigmas terete.

Capsules

7–9 mm, tomentose to lanulose.

1.8–4.5 mm, strigose-hispidulous.

Seeds

3.7–5 mm, smooth, lightly tuberculate, or striate.

1.5–2.4 mm, smooth, punctate, striate, or reticulate.

2n

= 26 (Baja California Sur, Mexico).

Argythamnia aphoroides

Argythamnia serrata

Phenology Flowering Jan–Jul. Flowering year-round.
Habitat Bluestem-grama grasslands, oak woodlands, calcareous, often rocky, clay or loam soils. Desert scrub, sandy, rocky, calcareous soils.
Elevation 300–600 m. (1000–2000 ft.) 0–1600 m. (0–5200 ft.)
Distribution
from FNA
TX
[BONAP county map]
from FNA
AZ; CA; NM; NV; TX; Mexico; Central America (Guatemala, Nicaragua)
[WildflowerSearch map]
[BONAP county map]
Discussion

Argythamnia aphoroides is restricted to the Edwards Plateau.

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

Argythamnia serrata is widely distributed and variable; six species have been described to recognize this variation. However, these groups overlap morphologically and geographically, and many specimens cannot be determined with confidence. A broadly defined A. serrata is therefore recognized here.

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

Source FNA vol. 12, p. 174. FNA vol. 12, p. 178.
Parent taxa Euphorbiaceae > Argythamnia Euphorbiaceae > Argythamnia
Sibling taxa
A. adenophora, A. argothamnoides, A. argyraea, A. brandegeei, A. claryana, A. cyanophylla, A. humilis, A. lanceolata, A. mercurialina, A. serrata, A. simulans
A. adenophora, A. aphoroides, A. argothamnoides, A. argyraea, A. brandegeei, A. claryana, A. cyanophylla, A. humilis, A. lanceolata, A. mercurialina, A. simulans
Synonyms Ditaxis aphoroides Aphora serrata, A. californica, A. dressleriana, A. gracilis, A. micrandra, A. neomexicana, A. serrata var. magdalenae, Ditaxis californica, D. dressleriana, D. gracilis, D. micrandra, D. neomexicana, D. odontophylla, D. serrata, D. serrata var. californica, D. serrata var. magdalenae
Name authority Müller Arg.: Linnaea 34: 146. (1865) — (as Argyrothamnia) (Torrey) Müller Arg.: Linnaea 34: 147. (1865) — (as Argyrothamnia)
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