Gymnosteris

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.

Phylogeny

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.

Biogeography

Gymnosteris is most abundant in the Great Basin.

worldwide distribution of  Gymnosteris

worldwide distribution of Gymnosteris

Taxonomy

  1. Gymnosteris nudicaulis (Hook. & Arn.) Greene
  2. 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

References

Wherry, E. T. 1944. Review of the genera Collomia and GymnosterisAmerican Midland Naturalist 31: 216–231.

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