Whole plant glabrous except for the reddish fringes along the midribs of the lower leaf-surfaces (rarely even these fringes wanting or rarely a few hairs at the base of the raceme). Foliage leaves mostly 2-3 cm. wide and 4.5-7 cm. long, 1.8-2.3 times as long as wide; leaves on individual plants sometimes smaller, or occasionally up to 4.5 cm. wide and 9 cm. long; l/w ratio more nearly constant in different leaves of the same plant than in P. serotina (typical), but in some plants standing at 2.7 or 2.8. Petioles very short (mostly 5-7 mm. long) in most Arizona material, longer (1-2 cm.) in most New Mexican and Texan plants and some Mexican material; blades with 4-11 (usually 5-7) teeth per cm. of margin. Second floral leaf mostly about 1.7 cm. wide and 3.4 cm. long, the l/w ratio usually about 2.0, but varying from 1.1 to 3.0; petioles averaging 0.7 cm. long (less- in the western part of the range); blades with 3-13 (usually 7) teeth per cm. of margin. Flowering branch averaging about 10 cm. long (longest branch noted was 39 cm.); flowers usually about 30 (greatest number observed, 69); pedicels about 3.5 mm. long in flower, 4.5 mm. in fruit (1.7-10 mm. in individual plants); calyx-lobes 1.2-2 mm. long (usually about 1.4-1.5 mm.); petals mostly about 3 mm. long and wide; longer filaments up to 3.5 mm. long; anthers averaging about 0.8 mm. long; style averaging about 1.4 mm. long (1-2 mm.); fruit about 1 cm. across.
Mountains, mostly above 1500 m. elevation, in arid and semi-arid ranges, usually in wooded canyons with other deciduous trees. From the Glass Mountains (Brewster County), Texas, west to the Hualpai Mountains (Mohave County), Arizona, and south to Coahuila, San Ldiis Potosi, Guanajuato and Jalisco. The only variety known to occur in Texas, northern Coahuila and southeastern New Mexico, but further south and west usually growing with the var. rufula.