Amer. J. Bot.83: 368. 1996
s, c, se United States, n Mexico.
Species 3 (3 in the flora).
R. L. Hartman (1990) informally recognized the three species of Rayjacksonia as an undescribed genus most closely related to Grindelia, Isocoma, Xanthocephalum, and other genera of Machaerantherinae with x = 6. The taxonomy was formalized by M. A. Lane and Hartman (1996). The Rayjacksonia species are coherent in vestiture, spinulose leaf teeth, heads borne singly, and rays with prominent, yellow laminae.
|1||Mid-cauline leaf blades linear to linear-oblanceolate, 1–3(–4) mm wide; involucres 4–7 × 10–15 mm; rays 14–19, corollas 6.5–9.5 mm||Rayjacksonia aurea|
|1||Mid-cauline leaf blades oblanceolate to oblong or oblong-lanceolate, (1–)4–15(–25) mm wide; involucres (4.5–)6–15 × 9–30 mm; rays (13–)17–38, corollas 6–19 mm||> 2|
|2||Heads on short, leafless or bracteate peduncles, not surpassed by distal leaves; mid-cauline leaf blades (1–)4–15(–25) mm wide; phyllaries in 3–4 series, strongly unequal, apices broadly spreading to squarrose, ca. 0.9–1 mm wide||Rayjacksonia annua|
|2||Heads essentially sessile, often surpassed by distal leaves that continue to very base of heads; mid-cauline leaf blades (2.5–)4–13 mm wide; phyllaries in 3–4 series, subequal, apices erect to spreading, 1.3–1.7 mm wide||Rayjacksonia phyllocephala|