Flora of North America species comparison

There is a historical record of Zeltnera exaltata from Montana. An old record from Nebraska is considered to be based on an adventive occurrence of short duration.

G. Mansion and L. Zeltner (2004) reported that plants compatible with descriptions of Zeltnera exaltata and similar in molecular characters included some populations with 2n = 40 and others with 2n = 74. They considered the latter likely to be of allopolyploid origin, derived from the hybridization of a diploid component of Z. exaltata in the narrow sense with a species having 2n = 34. Plants in the South Coastal Ranges from Baja California north to Monterey County, California, from which region Mansion and Zeltner reported 2n = 40, have smaller flowers, with the closed corollas 10–14 mm, subglobose seeds 0.25–0.33 mm in diameter, and pollen ca. 22 µm in diameter (C. R. Broome 1973). Plants (except those less than 10 cm) from localities farther inland and northward, from regions in which Mansion and Zeltner found 2n = 74, have corollas 14–20 mm, ellipsoid seeds 0.5–0.75 mm long, and pollen grains ca. 30 µm in diameter. By typification, the name Z. exaltata in the narrow sense is applicable to the entity occurring in the more northern and inland localities, with 2n = 74; if the species should be divided, it is the populations of the South Coastal Ranges, with 2n = 40, that should be treated as new. None of the names listed in the synonymy of Z. exaltata by Broome and Mansion (2004) is typified by specimens from the South Coast Ranges.

Zeltnera exaltata varies greatly in the number of stems arising from the base, the presence or absence of basal leaves at flowering time, and, especially in its easternmost populations, leaf width. The narrow angle of branching and the long pedicels generally give plants of this species a distinctive appearance. Its corollas are usually four-merous, whereas five-merous corollas prevail in the other Zeltnera species in the flora area (although four-merous corollas are not uncommon in Z. nudicaulis), and the corolla lobes, being about half as long as the tube, are proportionately shorter than those of the other Zeltnera species in the flora area. The four-merous corollas are useful in identifying very small plants of this species. The small corolla lobes are useful in distinguishing Z. exaltata from Z. multicaulis, which likewise has long pedicels but corolla lobes nearly as long as the tube.

In Nevada and adjacent regions of California, Zeltnera exaltata appears to intergrade with Z. namophila. As these species differ in chromosome number, additional chromosome counts and other techniques appropriate for the study of hybridization will be necessary for a satisfactory interpretation of apparent intermediates.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera ca. 100, species ca. 1800 (18 genera, 112 species in the flora).

In the tribal classification by L. Struwe et al. (2002), genera 1–7 in this flora are in tribe Chironieae Dumortier, subtribe Chironiinae G. Don. Species of Chironieae generally lack nectaries, although Sabatia reportedly has indistinct nectaries at the base of the ovary. Genera 8–17 are in tribe Gentianeae Dumortier. Gentiana, in which the nectaries are on the gynophore, is in subtribe Gentianinae G. Don; the remaining genera of the Gentianeae in the flora area, all of which have epipetalous nectaries, are in subtribe Swertiinae Grisebach. Voyria constitutes the monogeneric tribe Voyrieae Gilg, in which the nectaries (when present) are on the ovary or the gynophore.

Pedicel lengths given here refer to the true pedicels, between the most distal pair of bracts or bractlets and the calyx. In some genera, notably Centaurium, Sabatia, and Zeltnera, a flower terminating the ultimate branch of an inflorescence, directly subtended by bractlets, although sessile by this definition, may appear pedicellate. Corolla lengths as given are from the receptacle to the apices of the lobes (or plicae in Gentiana andrewsii).

The Gentianaceae include many species esteemed in ornamental horticulture. In addition to those noted under the respective genera, the more important species in North American horticulture include Exacum affine Balfour f. ex Regel, Persian-violet, native to the island of Socotra, Yemen, which is widely grown as a florists’ pot plant.

(Discussion copyrighted by Flora of North America; reprinted with permission.)