Stillingia

Herbs, subshrubs, or shrubs [trees], annual or perennial, monoecious; hairs absent [rarely glandular]; latex white. Leaves deciduous, alternate, opposite, or subopposite [whorled], simple; stipules absent or present, persistent; petiole absent or present, glands absent [small sessile gland at apex]; blade unlobed, margins entire, dentate, crenate, serrulate, or spinulose-dentate, laminar glands absent; venation pinnate. Inflorescences bisexual (pistillate flowers proximal, staminate distal), terminal, spikes or spikelike thyrses; glands subtending each bract 2. Pedicels absent. Staminate flowers: sepals 2, imbricate, connate basally; petals 0; nectary absent; stamens 2, connate basally; pistillode absent. Pistillate flowers: sepals 0 or [2–]3, distinct; petals 0; nectary absent; pistil [2–]3-carpellate; styles 3 [rarely 2], connate proximally, unbranched. Fruits capsules base persisting as [2–]3-lobed gynobase, glabrous. Seeds globose, ovoid, ellipsoid, or cylindric, ± flattened or depressed at hilar end; outer seed coat dry; caruncle absent or present. x = 11.

Distribution

s United States, Mexico, West Indies, Central America, South America, Indian Ocean Islands (Madagascar), Pacific Islands (Fiji Islands).

Discussion

Species ca. 33 (7 in the flora).

Stillingia is distributed primarily in the warmer regions of the western hemisphere, with a major center of diversity extending from the southwestern United States through Mexico to northern Central America and another occupying the region of southern Brazil, northern Argentina, and Paraguay. Other New World species occur in Peru, southern Central America, and the southeastern United States. Outside of the western hemisphere, there are three species in Madagascar and one in Fiji. Among species in the flora area, only S. sylvatica is widespread, ranging throughout much of the southern United States from Virginia to New Mexico.

Stillingia is one of the more distinctive genera in the tribe Hippomaneae A. Jussieu ex Spach, which are generally characterized by the presence of white latex and by terminal or axillary spikelike inflorescences with one or more solitary basal pistillate flowers. Among these genera, Stillingia is distinguished by the presence of a gynobase, the hardened proximal portion of the ovary that remains as a 3-parted (or 2-parted in a few species outside the flora area) persistent base attached to the pedicel after dehiscence of the fruit. The circumscription of Stillingia has remained essentially unchanged since 1880, when Bentham first recognized the importance of the gynobase as the most important distinguishing character (D. J. Rogers 1951).

Selected References

Rogers, D. J. 1951. A revision of Stillingia in the New World. Ann. Missouri Bot. Gard. 38: 207–259.

Lower Taxa

Stillingia aquatica, Stillingia linearifolia, Stillingia paucidentata, Stillingia spinulosa, Stillingia sylvatica, Stillingia texana, Stillingia treculiana

Key

1	Staminate flowers in 3–15-flowered cymules; sepals of pistillate flowers 3, well developed, persistent; seeds with caruncles.	> 2
2	Shrubs with taproots.	Stillingia aquatica
2	Herbs or subshrubs with woody caudices or rhizomes.	> 3
3	Leaf blades ovate, elliptic, or lanceolate, to obovate or oblanceolate, teeth without prominent blackened tips, incurved; capsules 6–12 mm diam.	Stillingia sylvatica
3	Leaf blades linear to linear-lanceolate, teeth with prominent blackened tips, not incurved; capsules 6–8 mm diam.	Stillingia texana
1	Staminate flowers 1 per node; sepals of pistillate flowers 0 or 3, minute and fugacious; seeds with or without caruncles.	> 4
4	Leaf blades linear, margins entire or remotely minutely denticulate.	> 5
5	Pistillate flowers widely spaced; glands of pistillate bracts long-stalked; seeds without caruncles.	Stillingia linearifolia
5	Pistillate flowers crowded; glands of pistillate bracts sessile; seeds with minute caruncles.	Stillingia paucidentata
4	Leaf blades elliptic, elliptic-spatulate, or obovate-spatulate, margins spinulose-dentate.	> 6
6	Leaves opposite or subopposite, stipules absent, blade apices acuminate; inflorescences sessile, 1–1.2(–2) cm; glands of pistillate bracts long-stalked; seeds without caruncles.	Stillingia spinulosa
6	Leaves alternate, stipules present, blade apices rounded to obtuse; inflorescences pedunculate, 2.5–5 cm; glands of pistillate bracts ± sessile; seeds with minute caruncles.	Stillingia treculiana