Stems densely bristly with spreading or slightly descending prickles 4–8 mm and mostly less than 0.5 mm diam. at base, 25+ per cm of stem, sparsely pubescent with short-stipitate glands. Calyx lobes 3.3–3.5 mm. Seeds with low, radially oriented ridges.

Phenology: Flowering Jul–Oct.
Habitat: Limestone, lava, sand, alluvial deposits, calcareous, gypseous, and saline flats, around wet depressions.
Elevation: 1100–1400 m.

Distribution

• Generated Map
• Legacy Map

Tex., Mexico (Chihuahua, Coahuila).

Discussion

Variety setigerum is found occasionally in Presidio County, where it is becoming a serious nuisance in overgrazed and irrigated lands.

Selected References

None.

Lower Taxa

None.