151a.  Dalea nana Torrey var. nana

(Plate CXXXVI)

Always diffuse or prostrate, the steins sometimes simple and monocephalous, more often branched; leaflets 5 in nearly all leaves, mostly obtuse or subobtuse, varying from densely silky-pilose to glabrescent above (but upper surface not verdigris- green when dried); calyx-teeth mostly 2.2-4.2 mm, keel-blades 3-4.8 mm long; n = 7 II (Mosquin).— Collections: 104 (viii).

Sandy plains, dunes, stream-beds, sometimes becoming weedy along roads and railroads, generally avoiding rocky subsoils and prevailingly calcifuge, 10-1500 m (25-5000 ft), locally abundant and widespread over the Gulf Coastal Plain of s. Texas and adjoining Tamaulipas and Nuevo Leon, absent or nearly so from Edwards Plateau and calcareous caprock of trans-Pecos, reappearing, but more scattered, on the plains of w. and panhandle Texas, n. through panhandle Oklahoma to the valleys of the Canadian and Arkansas rivers in s.-w. Kansas and s.-e. Colorado, w. through the middle Pecos valley to the Rio Grande (upstream to Albuquerque), and s. and s.-w. to Rio Conchos in centr. Chihuahua and around the s. end of the Mogollon massif in New Mexico into s.-e. Arizona; apparently absent from Coahuila, entering the Big Bend country only at its north margin and along the bed of Rio Grande, on the limestones of n. Mexico and w. Texas largely replaced by var. canescens. — Flowering April to September. — Representative: Colorado: Fremont (from La Junta) in 1845 (NY). Kansas: Rydberg & Imler 779, 975 (NY). Oklahoma: Waterfall 9052 (NY, OKLA); J. Engleman 969 (OKLA). New Mexico: R. T. Clausen 4617 (NY); Maguire 11,404 (NY, UC); Barneby 2479, 14,480 (NY). Arizona: Rusby 564 (NY, UC); Maguire 11,060 (NY); Thornber 4350 (UC). Texas: T. & L. Mosquin 5665 (NY); York & Rogers 17 (ENCB, OKLA); Ripley & Barneby 11,215 (NY), 14,508 (CAS, NY, US); Tracy 9081 (NY, WIS); R. Runyon 1398 (US). Chihuahua: Shreve 9061 (UC); A. R. Moldenke 2082 (RENNER). Nuevo Leon: Ripley & Barneby 14,784 (CAS, NY). Tamaulipas: Barkley 14,599 (F, NY, UC).

Dalea nana (dwarf) Torr. ex Gray, Mem. Amer. Acad. II, 4 (Pl. Fendl. 1): 31. 1849.—"[No. 130]. Sandy soil, Willow Bar, on the Cimarron; August." — Holotypus, collected by Fendler in 1847, GH!—Parosela nana (Torr.) A. Heller, Contrib. Herb. Franklin & Marshall Coll. 1: 49. 1895.

Racial differentiation in var. nana is apparently still active, expressed in small size- differences in the spikes and in length of the bracts, calyx-teeth, and androecia. Material from the upper Arkansas (nomenclaturally typical) and thence southwest to Rio Grande and on, sporadically, into extreme southeast Arizona, has relatively thick spikes (10-13 mm diam), long bracts (3.5-5.5 mm) and calyx-teeth (2.6-4.2 mm), and long androecia (mostly 8-10 mm). The populations on the Coastal Plain in southern Texas and adjoining Mexico, extending into central Texas, have narrower spikes (mostly 7-9 mm diam), and correspondingly short bracts (2.5-4, rarely 4.5 mm), calyx-teeth (2.2-3.4, rarely 3.8 mm), and androecia (6-8 mm). These differences represent, however, trends rather than accomplished modifications, coinciding for the most part with different life-zones, but are not yet fully stabilized.