Atrichoseris is a monotypic genus in the daisy family Asteraceae, containing only one species: Atrichoseris platyphylla, commonly known as tobacco weed, parachute plant, or gravel ghost. The genus is native to the desert regions of the southwestern United States — southern California, Arizona, Nevada, and the southwestern corner of Utah — and northwestern Mexico, including Sonora and Baja California.
The plant has a distinctive growth form: a low basal rosette of rounded leaves marked with gray-green and purple patches lies flat at ground level, from which a slender, branching stem rises to about 70 centimetres (28 inches). The stem is topped with numerous attractive, fragrant flowers that are white or lightly pink-tinged and roughly 2.5–5 cm (1–2 inches) wide. Each flowerhead is composed of layered ray florets that are rectangular and toothed at their tips. Flowering occurs between February and May. The hairless fruit is club-shaped with five distinct sides, and the absence of hairs on the fruit is the trait that gives the genus its name.
Etymology
The genus name Atrichoseris is derived from Greek and means "chicory plant without hairs" (a- = without, trichos = hair, seris = chicory/endive), referring to the hairless surface of the fruit. The specific epithet platyphylla means "flat-leaved," from Greek platys (broad, flat) and phyllon (leaf).
Distribution
Atrichoseris platyphylla grows in arid desert habitats across the southwestern United States, including southern California, Arizona, Nevada, and the southwestern corner of Utah, as well as northwestern Mexico in Sonora and Baja California.
Taxonomy Notes
Atrichoseris is a monotypic genus placed in the family Asteraceae (the daisy or composite family). GBIF accepts the genus with a single described species, Atrichoseris platyphylla. The genus name alludes to its morphological distinction from Seris (chicory) through the absence of hairs on the fruit.
