Part 3, 1918] ALLIONIACEAE 197 
11. AMMOCODON Standley, Jour. Wash. Acad. Sci. 6: 631. 1916. 
Erect or decumbent perennial herbs with thick woody roots, dichotomously much 
branched, pubescent. Leaves opposite, petiolate, those of a pair more or less unequal, the 
blades thick and fleshy, entire or sinuate. Flowers often cleistogamous, umbellulate, the 
umbellules in open cymes, each flower subtended by a minute subulate bract, or a second 
smaller bract rarely present; perianth campanulate, purplish red, constricted above the ovary, 
shallowly 5-lobed, the lobes induplicate-plicate. Stamens 2 or rarely 3; filaments filiform. 
short-connate at the base, free from the perianth; anthers didymous, exserted. Ovary nar- 
rowly oblong; style filiform, exserted; stigma peltate, smooth. Anthocarp compressed, broadly 
5-winged, the wings hyaline, not nerved. Seed with the testa adherent to the pericarp; 
embryo conduplicate, the cotyledons enclosing the farinaceous endosperm; radicle elongate, 
descending. 
Type species, Selinocarpus chenopodioides A. Gray. 
1. Ammocodon chenopodioides (A. Gray) Standley, Jour. Wash. 
Acad. Sci. 6: 631. 1916. 
Selinocarpus chenopodioides A. Gray, Am. Jour. Sci. IT. 15: 262. 1853. 
Plants 1.5-3 dm. high, much branched, the branches rather stout, when young densely 
covered with short appressed inflated white hairs, glabrate in age; petioles 0.5 to 4.5 cm. long; 
leaf-blades ovate-oval, oval, ovate-oblong, or rarely deltoid, suborbicular, or rhombic-orbicular, 
1.5-5 em. long, 0.6-4 cm. wide, rounded to subcordate at the base, broadly rounded to acute 
at the apex, often abruptly apiculate, flat or crispate, paler beneath, pubescent like the stems 
when young, becoming glabrate, the veins usually conspicuous beneath, broad and white; 
inflorescence much branched, bearing a few reduced leaves, the umbellules few- or many- 
flowered, the flowers on slender pedicels 1-4 mm. long; perianth 4-5 mm. long and fully as 
broad or broader, very shallowly lobed, sparsely puberulent outside; fruit 5 mm. long, the 
wings about 2 mm. broad, glabrate, the body sulcate between the wings, sparsely puberulent; 
seed oblong-cylindric, 2.5 mm. long, pale-brown. 
Type Locality: Valleys from Providence Creek to the Rio Grande, Texas. 
Distrisution: In dry, chiefly sandy soil, western Texas, southeastern Arizona, and Chihuahua. 
12. SELINOCARPUS A. Gray, Am. Jour. Sci. IT. 15: 262. 1853. 
Erect or decumbent perennial herbs or low shrubs, dichotomously much branched, pubes- 
cent. Leaves opposite, those of a pair more or less unequal, petiolate, the blades thick and 
succulent, entire or sinuate. Flowers perfect, pseudo-axillary, sessile or short-pedicellate, 
often cleistogamous, each subtended by 2 or 3 very narrow bracts; perianth tubular-funnel- 
form, the tube elongate or rarely short, not constricted above the ovary, rather abruptly 
expanded into a broad, shallowly 5-lobed limb, the lobes plicate. Stamens 5 or 6; filaments 
filiform, short-connate at the base, adherent to the perianth-tube; anthers didymous, usually 
exserted. Ovary oblong; style filiform, exserted; stigma peltate, smooth. Anthocarp com- 
pressed, broadly 3-5-winged, the wings hyaline, not nerved. Seed with the testa adherent to 
the pericarp; embryo conduplicate, the cotyledons enclosing the farinaceous endosperm; 
radicle elongate, descending. 
Type species, Selinocarpus diffusus A. Gray. 
Perianth 1 cm. long; leaf-blades linear or linear-oblong, sessile or short-petiolate.. 1. S. angustifolius. 
Perianth 2.5-4.5 cm. long. : 
Leaves long-petiolate, at least the lower ones, the blades ovate to orbicular. 
Upper leaves not reduced; fruit 6-7 mm. long. 2. S. diffusus, 
Upper leaves much reduced, bract-like; fruit 9-10 mm. long. 3. S. parvifolius. 
Leaves sessile or on very short petioles, the blades linear to narrowly ovate- 
oblong. 
Plants without glandular pubescence; leaf-blades 4-12 mm. wide, oblong- 
lanceolate to ovate-oblong. : 
Plants glandular-puberulent or glandular-hirtellous; leaf-blades less 
than 3 mm. wide, linear or spatulate-oblong. 
Leaf-blades linear, 1-4 cm. long, obscurely glandular-puberulent or 
labrous. 
eat blades narrowly spatulate-oblong, 4-11 mm. long, densely 
glandular-hirtellous. 
4. S. lanceolatus. 
5. S. Palmeri. 
6. S. Purpusianus, 
