Herbs annual, biennial, or perennial, chlorophyllous, glabrous or with peduncles and calyces papillate-scabridulous. Leaves basal (sometimes withering before flowering) and cauline, opposite. Inflorescences: flowers solitary or occasionally paired (G. barbellata), terminating main stem and each of any branches; peduncles or pedicels generally shorter than stem except in G. holopetala. Flowers 4-merous; calyx in most species with 2 outer lobes lanceolate, longer, narrower, and more strongly acute or acuminate than ovate inner lobes (nearly equal in size and shape in G. macrantha and G. simplex), margins of lobes narrowly hyaline at least in proximal 1/2, apices acute to acuminate, and with tube in most species ± as long as inner or all lobes (all lobes longer than tube in G. macrantha and sometimes in G. holopetala), not cleft and spathaceous; corolla blue or in most species occasionally rose-violet or white, rarely pale yellow, tube widely tubular or tubular-campanulate, adaxially glabrous or with minute trichomes near insertion of stamens, lobes spreading, often tardily reflexed, ± as long as or shorter than tube, margins usually distinctly toothed and/or fringed, rarely entire or nearly so, plicae between lobes absent, spurs absent; stamens inserted in proximal 1/2 of corolla tube; anthers distinct, not coiling; ovary subsessile or stipitate; style persistent, erect, short, indistinct or rarely slender and distinct; stigmas 2; nectaries 1 below each corolla lobe, on corolla tube near base. Capsules compressed-ovoid. x = [11], 13.

Distribution

North America, Mexico, Eurasia.

Discussion

Species ca. 15 (8 in the flora).

Gentianopsis has sometimes been treated as a subgenus or section of Gentianella, but molecular and other cladistic studies indicate that its distinctness and phylogenetic position are comparable to those of widely accepted related genera (Yuan Y. M. and P. Küpfer 1995; K. B. von Hagen and J. W. Kadereit 2001).

The taxonomic treatment of North American Gentianopsis has varied greatly in recent as well as in older literature. The combined history of misidentifications, different circumscriptions of taxa, and consequent difficulties in determining synonymy has resulted in erroneous or confusing statements as to the distribution of several of the taxa recognized here. This has also caused problems in determining their appropriate conservation status.

Some authors have assumed that North American Gentianopsis includes one group of taxa (the G. crinita complex) with x = 13 and another (the G. detonsa complex) with x = 11, but the occurrence of chromosomes in multiples of 11 in any North American Gentianopsis is unsub­stantiated and should be considered doubtful. Reports of 2n = 44 for taxa treated here as sub­species of G. detonsa and as G. thermalis have been based only on an early report of 2n = 44 for G. detonsa [subsp. detonsa] in Iceland, subsequently retracted (Á. Löve and D. Löve 1986); all of the more recent counts for G. detonsa, including those for Icelandic plants, are 2n = 78.

The subspecies of both Gentianopsis detonsa and G. virgata have often been treated as full species, but those within each of the respective more broadly defined species are so similar that specimens are sometimes difficult to identify except through consideration of their geo­graphic origin. Even taxa placed in different species in the treatment accepted here are less well differen­tiated than some references indicate and are occasionally difficult to distinguish. Differences are sometimes overstated, especially with regard to the shapes and proportions of the calyx lobes. Although isolated occurrences of one geographically restricted subspecies within the range of another would not be inconceivable, in this genus it is much more likely that the specimens on which such reports have been based represent morphological convergence due to environmental factors.

Gentianopsis taxa differ in the sizes of the largest plants and the largest flowers, but there is extensive overlap among taxa in the sizes of the smaller plants and their flowers. Likewise, the diagnostic value of the numbers and spacing of leaf pairs on the main axis is limited by variation in plant size and growing conditions. The lengths of the gynophores continue to elongate during the life of the flowers and as the fruits develop.

Gentianopsis species are generally restricted to more or less calcareous habitats. This is espe­cially evident in G. virgata subspp. macounii and virgata.

Selected References

None.

Lower Taxa

Gentianopsis barbellata, Gentianopsis crinita, Gentianopsis detonsa, Gentianopsis holopetala, Gentianopsis macrantha, Gentianopsis simplex, Gentianopsis thermalis, Gentianopsis virgata

Key

1	Flowers sessile or occasionally on peduncles to 0.7 cm; plants perennial.	Gentianopsis barbellata
1	Flowers on peduncles 0.7+ cm; plants annual or biennial, or seemingly biennial but with new stems arising from spreading roots in G. simplex.	> 2
2	Margins of corolla lobes entire or merely erose-undulate; peduncles mostly much longer than stem.	Gentianopsis holopetala
2	Margins of corolla lobes dentate, serrate, erose, or fringed; peduncles often shorter than stem.	> 3
3	Stems always simple even at base, 1-flowered; basal leaves withered at flowering; seeds striato-reticulate.	Gentianopsis simplex
3	Stems of most plants branched, 2–many-flowered (larger plants of some of these species occasionally accompanied by small, 1-flowered plants; such plants usually have basal leaves persistent at flowering time); seeds papillate.	> 4
4	Mid-stem and distal leaves lanceolate to ovate, apex acute; corolla lobes fringed on sides and around apex.	Gentianopsis crinita
4	Mid-stem and distal leaves linear or narrowly lanceolate to oblong-elliptic, elliptic, or oblanceolate (rarely ovate in G. thermalis, if so, apex ± obtuse); corolla lobes not fringed or fringed only on sides, apex merely dentate.	> 5
5	All or at least outer calyx lobes usually 1.5–2.5 times as long as or longer than calyx tube; branches, if present, from above base of primary stem rather than from base; s Arizona.	Gentianopsis macrantha
5	All or inner (shorter) calyx lobes less than 1.5 times as long as tube; branching from base of primary stem and/or higher; widely distributed in flora area, including Arizona.	> 6
6	All calyx lobes similar in size and shape, keels often ± undulate-crisped distally.	Gentianopsis thermalis
6	Outer calyx lobes narrower and more strongly acute or acuminate than inner, keels not undulate-crisped distally.	> 7
7	Branches or peduncles rarely arising from base; basal leaves usually withered at flowering; apices of mid-stem and distal leaves acute; calyx keels usually papillate- or granular-scabridulous proximally (seen at 50×), occasionally nearly smooth.	Gentianopsis virgata
7	Branches and/or peduncles often arising from base as well as distally; basal leaves usually persistent and green at flowering; apices of all leaves obtuse, acute in subsp. detonsa; calyx keels smooth.	Gentianopsis detonsa