Ambrosia canescens A. Gray

Franseria canescens (Benth.) Rydberg
Ambrosia fruticosa var. Benth. PI. Hartw. 17. 1839.
Ambrosia fruticosa canescens Benth.; Hemsl. Biol. Centr. Am. Bot. 2: 150. 1881.
Ambrosia canescens A. Gray, Proc. Am. Acad. 17: 217. 1882.
A perennial herb, with a rootstock; stem 3-5 dm. high, sparingly strigulose or glabrate; leaves short-petioled, tripinnatifid, densely white-strigulose on both sides or merely grayish above; blades ovate, oval, or obovate in outline, 3-10 cm. long; segments divergent, the ultimate ones linear or linear-oblong, acute; inflorescence rather simple, racemose or with a fewbranches; staminate heads reflexed on spreading peduncles, which are about 3 mm. long; involucre about 4 mm. wide, finely strigulose; lobes 8-10, rounded-ovate; paleae of the receptacle linear or filiform, with rhombic or broadly spatulate tips, or sometimes spatulate; pistillate heads in small clusters in the upper axils and on the lower part of the staminate raceme, 1flowered; fruit 5-6 mm. long, glandular-puberulent, reticulate-rugose; beak solitary, conic; spines 8-15, in 2-3 series, dilated below, but not strongly flattened, some of them more or less hooked.
Type locality: Aguascalientes.
Distribution: Chihuahua to Queretaro and state of Mexico.