STANDLEY—ALLIONIACEAE OF THE UNITED STATES, 305 
SYSTEMATIC TREATMENT. 
ALLIONIACEAE Reichenb. Consp. 85. 1828. 
Nyctaginaceae Lindl, Nat. Syst. ed. 2. 213. 1836, 
Annual or perennial herbs, often shrubs or trees, with branching or dichoto- 
mous-forking stems; stems usually with swollen joints, sometimes armed with 
spines; leaves opposite or alternate, simple, entire, or sometimes repand, 
exstipulate; inflorescence various; flowers regular, perfect or sometimes uni- 
sexual, often subtended by bracts which form a calyx-like involucre; perianth 
consisting of a calyx only, this often showy and corolla-like, tubular, funnel- 
form, or campanulate, usually deciduous above the ovary ; stamens 1 to many; 
filaments filiform, distinct or united at the base, often unequal in length, ex- 
serted or ineluded: anthers 2-celled, opening by longitudinal fissures; ovary 
1-celled, superior but surrounded by the calyx tube, sessile or short-stalked ; 
style slender; stigma usually capitate; ovule solitary, erect, sessile; fruit an 
anthocarp, indehiscent, fleshy, leathery, or hard, angled, ribbed, grooved, or 
winged: seed erect, with a hyaline testa which is free from or adnate to the 
pericarp; endosperm variable; embryo straight or curved, 
The fhmily consists of about 26 genera and 250 species. Most of the genera 
and species are confined to the Western Hemisphere. In the Old World there are 
found one species of Allionia, several of Boerhaayvia and Pisonia, and the mono- 
typic South African genus Phaeoptilon, Of these only one, a species of Boer- 
haavia, occurs in Europe (in southern Spain), the others being confined to 
Africa, southern and eastern Asia, and the islands of the Pacific. Doctor 
Heimerl mentions the fact that one or two American species have become 
naturalized at various places in Europe. 
In the Western Hemisphere there seem to be two centers of distribution, one 
in tropical and subtropical South America and the West Indies, characterized 
by such genera as Pisonia, Neea, Bougainvillea, and others; the other in 
‘fexus, New Mexico, Arizona, California, and northern Mexico, especially 
characterized by such genera as Boerhaavia, Abronia, Acleisanthes, Allionia, 
but presenting several others. Of the entire number of genera included in 
the family 16 occur in the latter region ewbracing more than 160 species. It 
is the region about this center that this paper attempts to cover. 
KEY TO THE GENERA. 
Flowers involucrate. 
Involucre polyphyllous, composed of 5 to 15 
bracts which surround a few-flowered or many- 
flowered head. 
Fruit winged or at least with rudimentary 
wings; bracts few; stamens and pistil in- 
cluded. 
Wings not completely encireling the fruit 
but interrupted above and below__-~- 
Wings completely encircling the fruit_- 
Fruit not winged but merely 10-ribbed; 
bracts more numerous; stamens and pistil 
exserted ~~ ~~ ~~ ~~ ++ -- 3B. NYCTAGINIA (p). 330), 
Involucre gamophylous; flowers 1 to several. 
Fruit with prominent lateral wings which 
are often toothed; with 2 rows of glands 
along the dorsal surface____----~--~--- _ 4, WrEDELIA (p. 551). 
. ABRONIA (p. 806). 
2. TRIPTEROCALYX (p. 327). 
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