Oenothera parryi S. Watson, Amer. Naturalist 9: 270. 1875; Camissonia parryi (S. Watson) P. H. Raven; Chylismia tenuissima (M. E. Jones) Rydberg; O. scapoidea Torrey & A. Gray var. parryi (S. Watson) M. E. Jones; O. tenuissima M. E. Jones

Herbs annual, sparsely to densely villous throughout or, sometimes, glabrate distally. Stems often intricately branched, 5–80 cm. Leaves in poorly defined basal rosette and also cauline; petiole 0.3–3.8 cm; blade usually unlobed, very rarely pinnately lobed with few, small lateral lobes, ovate to elliptic, margins sparsely denticulate to subentire, pale or dark brown oil cells lining veins abaxially. Racemes nodding, with intricate, filiform branches, elongating in fruit. Flowers opening at sunrise; buds without free tips; floral tube 0.5–2 mm, glabrous or villous inside; sepals 1.5–4 mm; petals bright yellow, often with red dots near base, fading pale yellow or yellowish orange, 2–7 mm; stamens unequal, filaments of antisepalous stamens 1.7–3.5 mm, those of antipetalous ones 1.2–2.5 mm, anthers 0.9–1.2 mm, glabrous; style 4–9 mm, stigma exserted beyond anthers at anthesis. Capsules erect or ascending, clavate, 4–10 mm; pedicel 4–20 mm. Seeds 0.7–1.2 mm. 2n = 14.

Flowering May–Jun(–Sep). Red clay and sand slopes weathered from red (freshwater-deposited) sandstone cliffs, with Juniperus or Larrea tridentata; 800–1300 m; Ariz., Utah.

Chylismia parryi is known from northwestern Arizona (Coconino to Mohave counties) and southwestern Utah (Beaver to Washington counties), and is apparently disjunct to San Juan County, Utah. It is outcrossing and, perhaps, self-incompatible (P. H. Raven 1962, 1969). There are two morphological forms of this species. Raven (1962) noted that a later flowering form has narrower, smaller leaves, and less overall pubescence. It is not clear what these represent, but Raven (1962) made the combination Oenothera parryi forma tenuissima (M. E. Jones) P. H. Raven for it. He later (Raven 1969) noted that these plants did not seem to merit formal recognition, without any discussion.