Pisonia capitata (S. Wats.) Standl.

Pisonia capitata is represented in the flora by a single, possibly clonal, population of a few pistillate plants in south-central Arizona several hundred kilometers north of known populations in Sonora, perhaps originating from a freak event of bird dispersal. Plants are not known to have set seed.

As noted above, pistillate plants of Pisonia capitata and P. aculeata exhibit no apparent differences, nor are there apparent vegetative differences between the species. That plants known in the flora truly represent P. aculeata is an assumption based on geography.

Shrubs or small trees, to 6 m; branches dense, spreading at right angles, usually armed with stout, recurved spines 7-14 mm. Stems arching, velvety when young, glabrate later. Leaf blades broadly obovate or suborbiculate, 2-6 × 2-6 cm, base rounded or broadly cuneate, apex rounded, rarely subacute. Inflorescences: [staminate inflorescences subglobose, dense, 1-2 cm diam.]; pistillate inflorescences densely subglobose at anthesis, more open in age; branches divaricate or ascending; fruiting pedicel 0.5-2 cm. Perianths: [perianth of staminate flowers deep red, broadly campanulate, 2-3 mm, densely and shortly viscid-villous]; perianth of pistillate flowers greenish, often blushed with red, 2-2.5 mm, densely puberulent. Fruits clavate, 7-10 × 3-4 mm, densely puberulent between glandular ribs, glands extending entire length of fruits.

Ariz.; nw Mexico.

Flowering winter-early spring.

Protected clefts on rhyolitic soils in arid scrub [tropical deciduous forests, thickets, along watercourses]; 0-1100m.

Cryptocarpus capitatus S. Watson, Proc. Amer. Acad. Arts 24: 71. 1889

Pisonia capitata (S. Wats.) Standley, Contr. U. S. Nat. Herb
13: 388. 1911.
Cryptocarpus ? capitatus S. Wats. Proc. Am. Acad. 24: 71. 1889.
A densely branched shrub or small tree, 5 meters high or less, branched to the ground or often with a distinct trunk, the branches spreading or often weak and clambering, armed with numerous stotit, recurved or rarely straight spines 7-14 mm. long; branches stout, terete, gray or greenish-gray, sometimes reddish-brown, the branchlets densely shortvillous ; petioles slender or stout, 0.6-3 cm. long; leaf-blades orbicular or orbicular-obovate, 2-6 cm. long and nearly or quite as broad, rounded to broadly cuneate at the base, broadly rounded at the apex, or sometimes very shortly and abruptly acutish, thick and firm, dull, yellowish-green, densely and finely puberulent on the upper surface, densely puberulent or very shoitvillous beneath, the margins plane, the lateral veins often conspicuous beneath, divaricate or ascending; peduncles of the staminate inflorescence solitary, stout, 0.5-3 cm. long, the cymes subglobose, congested, densely many-rlowered, 1-1.8 cm. in diameter, the flowers on very short, densely puberulent pedicels, the perianth broadly campanulate, 2-3 mm. long, densely and shortly viscidvillous, deep-red, the lobes obtuse; stamens 6, twice as long as the perianth; pistillate peduncles 0.5-2 cm. long at an thesis, 4 cm. long or less in fruit, the cymes at an thesis subglobose, densely flowered, in age loosely branched, the branches divaricate or ascending, the pedicels at first 1-2 mm. long, in age 0.5-2 cm. long, the bractlets subulate-linear, 1 mm. long, the perianth tubular, 2-2.5 mm. long, densely puberulent, shallowly 5-dentate; fruit clavate or prismatic, 7-10 mm. long, 3-4 mm. in diameter, rounded at the apex, narrowed at the base, 5-angled, each angle furnished with a row of low uniseriate glands, the sides densely puberulent; seed cylindric, 6-8 mm. long, 1.5 mm. in diameter, dark-brown.
Type locality: Near Guaymas, Sonora.
Distribution: In sandy soil, often along watercourses, southern Sonora to Tepic.