Flora of North America species comparison

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Argythamnia

silverbush, wild-Mercury
Habit Herbs, subshrubs, or shrubs [trees], annual or perennial, monoecious or dioecious; hairs usually malpighiaceous (appressed and attached by the middle), sometimes unbranched [stellate], rarely absent; latex absent.
Leaves

drought deciduous or persistent, alternate, simple;

stipules present, persistent or deciduous;

petiole absent or present, glands usually absent (tack-shaped glands along length in A. adenophora);

blade unlobed, margins entire or serrate-dentate, laminar glands absent;

venation palmate (3- or 5-veined), secondary veins arcuate, not closely spaced.
Inflorescences

unisexual or bisexual (pistillate flowers proximal, staminate distal), axillary, racemes;

glands subtending each bract 0.
Pedicels

present.
Staminate flowers

sepals [4–]5, valvate, distinct;

petals [4–]5, distinct, free or adnate to androphore, white, sometimes pale yellow-green or pale purple proximally;

nectary extrastaminal, [4–]5 glands;

stamens [4–](7–)10[–12] in [1–]2 whorls, connate proximally forming androphore;

staminodes 0–5, at apex of androphore;

pistillode absent.
Pistillate flowers

sepals 5, distinct;

petals usually 5, sometimes rudimentary or 0, distinct, white, sometimes pale yellow-green or pale purple proximally;

nectary 5 glands;

pistil 3(–4)-carpellate;

styles 3, distinct or connate proximally, 2-fid, branches 6 per flower, [2 times 2-fid].
Fruits

capsules, not muricate.
Seeds

globose to ovoid;

caruncle absent [present].

Argythamnia
Distribution
from USDA
United States; Mexico; Central America; South America; West Indies; tropical and subtropical regions
[BONAP county map]
Discussion

Species ca. 80 (12 in the flora).

There has been controversy surrounding the taxonomic status of Argythamnia. Some authors have recognized Ditaxis, which includes all of the species in the flora area, at the generic level (G. L. Webster 1994b; A. Radcliffe-Smith 2001), whereas others have treated it as a subgenus of Argythamnia (J. W. Ingram 1980; R. McVaugh 1995). There are several morphological characters that distinguish these taxa and pollen morphology supports their generic recognition (W. Punt 1962). However, recent molecular phylogenetic studies demonstrate that recognizing Ditaxis makes Argythamnia paraphyletic (Y. Ramírez-Amezcua 2011), so they are treated here as a single genus.

Argythamnia heterantha (Zuccarini) Müller Arg., from Mexico, is cultivated; the seeds are used as a saffron substitute and represent a potential resource for dye, oil, and protein (M. D. Méndez-Robles et al. 2004).

M. C. Johnston (1990) reported Argythamnia astroplethos J. W. Ingram from the Chinati Mountains, Presidio County, Texas, but no specimens were cited and none have been located. This species grows nearby in Chihuahua, Mexico, and may eventually be documented from Texas. It belongs to subgenus Chiropetalum (A. Jussieu) J. W. Ingram and can be distinguished from other Argythamnia species in the flora area by its indumentum of stellate hairs in addition to malpighiaceous hairs, tetramerous staminate flowers, and styles that are twice 2-fid.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Glands present on margins of stipules, leaf blades, bracts, and pistillate sepals.
→ 2
2. Stems and leaves with simple hairs; margins of stipules, leaf blades, bracts, and pistillate sepals with tack-shaped glands.
A. adenophora
2. Stems and leaves with simple and malpighiaceous hairs; margins of stipules, leaf blades, bracts, and pistillate sepals with conic glands.
A. claryana
1. Glands absent on margins of stipules, leaf blades, bracts, and pistillate sepals.
→ 3
3. Petioles usually absent, rarely to 4 mm on proximal leaves.
→ 4
4. Pistillate petals 5, 2.8–3.5 mm, obovate to spatulate; stipules punctiform.
A. cyanophylla
4. Pistillate petals 0 or 5, 0–1.7 mm, elliptic, lanceolate, linear, or punctiform; stipules elliptic, ovate, subulate, or linear-lanceolate.
→ 5
5. Nectary glands of pistillate flowers linear, of staminate flowers linear to obovate.
A. mercurialina
5. Nectary glands of pistillate and staminate flowers ovate or oblong.
→ 6
6. Stamens 10; staminate petals cuneate-elliptic to cuneate-obovate; ovary tomentose to lanulose.
A. aphoroides
6. Stamens 7–8; staminate petals elliptic; ovary strigose to hispidulous.
A. simulans
3. Petioles present, 1–18 mm.
→ 7
7. Plants dioecious.
→ 8
8. Flowers usually releasing pink dye when wetted; styles pilose; staminate nectary glands 0.1–0.2 × 0.1 mm; stems and leaves densely hairy, hairs silvery.
A. argyraea
8. Flowers without pink dye when wetted; styles glabrous; staminate nectary glands 0.3–1 × 0.2–0.4 mm; stems and leaves hairy or glabrous, hairs silvery or not.
→ 9
9. Staminate petals free from androphore; pistillate petals elliptic to filiform, 0.3–1.7 × 0.3–0.4 mm.
A. humilis
9. Staminate petals adnate to androphore; pistillate petals elliptic, 1.8–3 × 0.7–1.4 mm.
A. lanceolata
7. Plants monoecious.
→ 10
10. Staminate petals adnate to androphore.
→ 11
11. Inflorescences 1.5–5.5 cm; staminate sepals 4–6 × 0.8–1 mm; staminate petals 5–7 × 1.2–2.5 mm; pistillate petals 5–6 × 1.5–1.6 mm; petioles 7–18 mm.
A. brandegeei
11. Inflorescences 0.4–1.3 cm; staminate sepals 2–3 × 0.5–0.8 mm; staminate petals 2.1–3.4 × 0.7–1.2 mm; pistillate petals 1.5–3 × 0.6–1.4 mm; petioles 1–5 mm.
→ 12
12. Stigmas terete or slightly flattened; pistillate petals 1.5–1.8 × 0.6–1 mm; Florida.
A. argothamnoides
12. Stigmas flattened; pistillate petals 1.8–3 × 0.7–1.4 mm; Arizona, California.
A. lanceolata
10. Staminate petals free from androphore.
→ 13
13. Stigmas terete; staminate sepals 0.9–2.5 mm.
A. serrata
13. Stigmas flattened; staminate sepals 2–5 mm.
→ 14
14. Flowers usually releasing pink dye when wetted; staminate nectary glands ovate, 0.1–0.2 × 0.1 mm.
A. argyraea
14. Flowers not releasing pink dye when wetted; staminate nectary glands ovate to linear, 0.4–0.8 × 0.2–0.3 mm.
A. humilis
Source FNA vol. 12, p. 172. Author: Yocupitzia Ramírez-Amezcua.
Parent taxa Euphorbiaceae
Subordinate taxa
A. adenophora, A. aphoroides, A. argothamnoides, A. argyraea, A. brandegeei, A. claryana, A. cyanophylla, A. humilis, A. lanceolata, A. mercurialina, A. serrata, A. simulans
Synonyms Aphora, Ditaxis, Serophyton
Name authority P. Browne: Civ. Nat. Hist. Jamaica, 338. (1756)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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