Gymnosteris is a small genus of two species of diminutive annuals native to western North America. The genus is remarkable not only in its small size but that it lacks true leaves. All photosynthesis is conducted by the two persistent cotyledons as well as the large bracts surrounding the inflorescence.
Gymnosteris are unique in Polemoniaceae in that it only has the fewest number of chromosomes (n=6). Molecular evidence places the genus as sister to a clade comprised of Microsteris, Phlox, and Leptosiphon.
Gymnosteris is most abundant in the Great Basin.
- Gymnosteris nudicaulis (Hook. & Arn.) Greene
- Gymnosteris parvula A. A. Heller
KEY TO GYMNOSTERIS (modified from Wherry (1944)).
1. Plant up to 15 cm tall; calyx up to 5 mm long; corolla tube 6-10 mm long, the lobes 3-6 mm long……Gymnosteris nudicaulis
1. Plant less than 8 cm tall; calyx up to 4 mm long; corolla tube 2.5-5 mm long; the lobes 0.7-1.5 mm long……Gymnosteris parvula
Wherry, E. T. 1944. Review of the genera Collomia and Gymnosteris. American Midland Naturalist 31: 216–231.