55. Helminthotheca Zinn, Cat. Pl. Hort. Gott. 430. 1757.
Oxtongue [Greek helminthos, worm, and Latin theca, case or container; allusion unclear, perhaps to shapes of cypselae]
John L. Strother
Annuals or biennials, 10–100+ cm; taprooted. Stems usually 1, erect, branched distally or throughout, hirsute to hispid or setose (hair tips 2–4-hooked). Leaves basal and cauline; basal ± petiolate, distal sessile; blades elliptic, lanceolate, oblanceolate, oblong, or ovate, margins usually dentate to pinnately lobed (faces hirsute to hispid, hair tips 2–4-hooked). Heads borne singly or in loose, corymbiform arrays. Peduncles (terminal and axillary) not inflated distally, seldom bracteate. Calyculi of (3–)5, cordate or ovate to lance-ovate, foliaceous bracts. Involucres ovoid to urceolate, 9–12+ mm diam. (larger in fruit). Phyllaries (5–)8–13+ in 1 series, lance-linear to linear, subequal, margins little, if at all, scarious, apices acuminate. Receptacles flat, pitted, glabrous, epaleate. Florets 30–60+; corollas yellow (often reddish abaxially). Cypselae (dimorphic): outer whitish, bodies gibbous, ribs 5–10, beaks about equaling bodies, fragile, faces hirtellous to pilosulous adaxially; inner reddish brown, bodies ± compressed-ellipsoid to fusiform, beaks about equaling or longer than bodies, fragile, faces transversely rugulose to muricate, otherwise glabrous; pappi persistent, of 10–15+, whitish, subequal, barbellate or plumose, subulate to setiform (basally connate) scales in 1–2 series. x = 5.
Species 4 (1 in the flora): introduced; Europe; widely introduced.
Lack, H. W. 1975. A note on Helminthotheca Zinn (Compositae). Taxon 24: 111–112.