This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial, erect, branched, 6'-2° high, more or less hispid, pubescent or canescent. Leaves lanceolate or oblanceolate in outline, sessile or the lowest petioled, 6"-2' long, usually finely and deeply pinnatifid into linear-oblong lobes; flowers axillary, white, turning pink, q"-I5" broad; calyx-segments linear, the tips free in the bud, reflexed, the throat villous within; petals broadly obovate; capsules oblong, abruptly constricted at the top, straight, pubescent and sometimes tuberculate, 4"-10" long, about 2" thick; seeds tuber-culate.
Oe. albicaulis Nutt. Fras. Cat. Name only. 1813.
A. Nuttalliana Spach, Ann. Sci. Nat. II. 4: 164. 1835.
Perennial, erect, simple or branched, 6-3o high, stems white or pale, glabrous, rarely with a few scattered long hairs, the bark often shreddy. Leaves linear, sessile or the lowest petioled, finely appressed-pubescent beneath, glabrous above, entire or sparingly denticulate, 1'-3 1/2 long; flowers axillary, white, turning pink, 1'-1 1/2' broad; segments of the calyx linear, the tips free in the bud, its throat glabrous within; petals nearly orbicular, entire or emarginate; capsules linear, erect-ascending, 1-1 1/2' long, about 1 1/2" thick; seeds smooth.
Prairies, Minnesota to Saskatchewan, British Columbia, Nebraska and Colorado. White shrubby evening primrose. June-Aug. Included in the western A. pallida in our first edition.
Oenothera pallida latifolia Rydb. Contr. U. S. Nat. Herb. 3:
159. 1895. Anogra latifolia Rydb. Bull. Torr. Club 31: 570. 1904.
Perennial, often much branched, 2° high or less, the stout branches canescent, ascending. Leaves lanceolate to oblong, firm in texture, 2-4' long, 1/4'-1 1/4' wide, acute, sinuate-dentate, or sometimes nearly entire, ashy-canescent on both sides; flowers axillary, white, turning pink, 1 1/4'-2' wide; calyx strigose without; tips of the calyx-segments free in the bud; calyx-throat glabrous within; capsules linear, 1'-2' long, widely spreading or somewhat upcurved.
Dry soil, Nebraska and Kansas to Utah and New Mexico. June-Aug.