Genus 2. 



FOUR-O'CLOCK FAMILY. 



33 



2. ABRONIA Juss. ; Gmel. Syst. 1008. 1791. 



Annual or perennial herbs, with opposite petioled thick entire leaves, one of each pair 

 somewhat larger than the other. Stems ascending, erect or prostrate, branching, mostly 

 glandular-pubescent, with clustered or solitary numerous-flowered involucres on long 

 axillary peduncles. Flowers sessile, usually conspicuous. Perianth-tube elongated, tubular 

 or funnelform, the limb spreading, 5-lobed, the lobes obcordate or emarginate. Stamens 3-5, 

 unequal, inserted on the tube of the perianth ; anthers linear-oblong, included. Style 

 filiform. Fruit dry, 1-5-winged or ridged, the wings broad or narrow, reticulate-veined. 

 Seed cylindric, smooth, shining; one of the cotyledons is abortive, the seedling appearing 

 monocotyledonous. [Name from the Greek, graceful.] 



About 45 species, all American, mostly of western North America. Type species: Abronia 

 californica Gmel. 



I. Abronia fragrans Nutt. White Abronia. 

 Fig. 1 73 1. 



Abronia fragrans Nutt. ; Hook. Kew Journ. Bot. 5 : 

 261. 1853. 



Perennial, viscid-pubescent, stem erect or as- 

 cending, usually much branched, i°-2° high. 

 Leaves oval, ovate or oblong-elliptic, petioled, 

 obtuse or acutish at the apex, cuneate, truncate 

 or rounded at the base, i'-2i' long; bracts of the 

 involucre 5 or 6, ovate or elliptic, white, 5"-8" 

 long ; flowers greenish-white, very numerous in 

 the involucres, 8"-i2" long, fragrant, opening at 

 night; fruit 4"-6" high, coriaceous with 5 or 

 sometimes fewer, undulate coarsely reticulated 

 ridges about i" wide, which do not close over its 

 summit. 



In dry soil. South Dakota to Nebraska, Colorado, 

 Texas and Mexico. Reported from Iowa. June-Aug. 



3. TRIPTEROCALYX [Torn] Hook. Kew Journ. Bot. 5: 261. 1853. 



Annual much-branched herbs, more or less pubescent with flattened hairs, with opposite, 

 usually unequal leaves, and axillary or lateral long-peduncled involucres subtending numer- 

 ous pink or whitish flowers, the involucral bracts separate. Perianth-tube elongated, the 

 limb S-lobed. Stamens 5, inserted on the perianth-tube; filaments short. Fruit dry, leathery, 

 completely encircled by 2 to 4 broad reticulated membranous wings. [Greek, three-winged 

 calyx.] 



About 5 species, natives of western North America, the following the generic type. 



I. Tripterocalyx micranthus (Torr.) Hook. 

 Pink Abronia. Fig. 1732. 



Tripieridium micranthum Torr. Frem. Rep. g6. i845> 



Abronia micrantha Chois. in DC. Prodr. 13 : Part 2, 

 436. 1849. 



Tripterocalyx micranthus Hook, Kew Journ. Bot. 5 : 

 261. 1853. [By typographical error macranthus.'i 



Annual, glabrous below, more or less glandular- 

 pubescent above, stem ascending, branched, i°-2° 

 high. Leaves quite similar to those of Abronia 

 fragrans in size and outline; involucral bracts 

 ovate or ovate-lanceolate, acute or acuminate; 

 flowers several or numerous, about 6" long, 

 greenish-white; calyx-limb about 4" broad; fruit 

 nearly l' high, its 2-4 membranous wings 4"-?" 

 broad, entire-margined, shining, very conspicuous, 

 glabrous, united over the body of the fruit, beauti- 

 fully reticulate-veined. 



In dry soil, South Dakota to Montana, Nevada, 

 Kansas and New Mexico. June-Aug. 



