195c. Xanthisma de Candolle sect. Sideranthus (Nuttall ex Nees) D. R. Morgan & R. L. Hartman, Sida. 20: 1405. 2003.
Sideranthus Nuttall ex Nees in M. P. zu Wied, Reise Nord-America 2: 440. 1841; Machaeranthera Nees sect. Sideranthus (Nuttall ex Nees) R. L. Hartman; Machaeranthera sect. Stenoloba R. L. Hartman
Annuals, perennials, or subshrubs, 3–80 cm; taprooted, sometimes with much branched caudices. Leaf blades entire, serrate, dentate, or pinnatifid to deeply 2-pinnatifid, teeth or lobes usually bristle-tipped, often markedly so. Heads radiate. Involucres broadly turbinate to depressed campanulate or hemispheric. Phyllaries in 4–8 series, appressed to squarrose, light green to stramineous, linear to narrowly oblong, 1–2 mm wide, unequal, proximally rigid, distal 1 / 5 – 1 / 2 with green patch or strip (sometimes blackish near apices), not markedly expanded, apices obtuse to acuminate, usually stiffly, often markedly bristle-tipped, faces usually hairy, often stipitate-glandular. Receptacles: pit borders laciniate, teeth or setae distinct or basally connate, 0.4–3 mm. Ray corollas yellow. Cypselae often dimorphic, ellipsoid to broadly obovoid, or obscurely and narrowly cordiform, ray obscurely 3-sided (usually rounded on abaxial edge, often asymmetric, slightly shorter), disc flattened laterally, 1.5–3.2 mm, walls thin, 6–16-ribbed, usually weak, sometimes prominent, faces glabrous to densely silky; pappi of white to tawny, slightly to moderately dorsiventrally, basally flattened bristles 3.5–6 mm, in 2–4 markedly unequal series, ray sometimes shorter. x = (2, 3,) 4.
Species 6 (3 in the flora): w North America, Mexico.
