Gentianaceae

Herbs [shrubs, trees], annual, biennial, or perennial, autotrophic, with green stems and leaves, or mycotrophic; when strongly mycotrophic, stems and leaves weakly chlorophyllous (only in Bartonia) or yellowish, whitish, purplish, or buff, or lacking chlorophyll (only in Voyria). Leaves cauline, often also basal, opposite, whorled, or rarely alternate, sessile or petiolate, simple; stipules absent [rarely present as ocreae]; blade margins entire. Inflorescences cymes (sometimes racemoid, spicoid, or capitate), thyrses, or verticillasters, or solitary flowers; flowers pedicellate or sessile. Flowers bisexual or occasionally some unisexual [all unisexual on some or all plants], homostylous [heterostylous], protandrous and outbreeding or less often homogamous and autogamous, radially [somewhat bilaterally] symmetric, 4–12(–14)-merous [rarely 3-, 6-, or 16-merous] except for carpels; perianth hypogynous, calyx and usually corolla persistent; calyx green or occasionally ± hyaline (absent in Obolaria), sepals connate or some [or all] nearly distinct, lobes imbricate in bud, often ± unequal, colleters often present adaxially near base; corolla petaloid, petals connate, lobes contorted in bud or rarely imbricate (Obolaria, Voyria), spurs present only in Halenia, 1 per petal; stamens epipetalous, isomerous and alternate with petals, all fertile [rarely some sterile], equal [unequal]; filaments free or connected by a corona; anthers 2-locular, dehiscing longitudinally [with terminal pores], remaining straight, recurving, or coiling helically or circinately, distinct or (only in some spp. of Gentiana) coherent; pistil 1, 2-carpellate; ovary 1[or 2]-locular; placentae 2, parietal [axile]; style present or absent, erect or initially deflexed to one side [declinate], uncleft, shallowly 2-cleft, or deeply cleft (Sabatia); stigmas 1 or 2, coiling only in Sabatia, decurrent on ovary (only in Lomatogonium, sometimes slightly so in Bartonia). Fruits capsular, dehiscence septicidal or rarely rupturing irregularly (Obolaria) [indehiscent capsules, berries]. Seeds few–very many, usually sessile; endosperm abundant and embryo small in autotrophic species, endosperm scant and embryo undifferentiated in completely mycotrophic species (Voyria).

Distribution

nearly worldwide.

Discussion

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.

Selected References

None.

Lower Taxa

Bartonia, Centaurium, Cicendia, Comastoma, Eustoma, Frasera, Gentiana, Gentianella, Gentianopsis, Gyrandra, Halenia, Lomatogonium, Obolaria, Sabatia, Schenkia, Swertia, Voyria, Zeltnera

Illustrations

Gentianaceae Illustrations

Key

1	Corollas with 4 spurs.	Halenia
1	Corollas without spurs.	> 2
2	Leaves and stems yellowish, whitish, purplish, or buffy, without chlorophyll or weakly chlorophyllous; leaves scalelike, blades to 5 mm.	> 3
3	Stems and leaves yellowish green or purplish; corollas narrowly campanulate, lobes 4, longer than tube; widely distributed in c, e North America (including Florida).	Bartonia
3	Stems and leaves white to pale buff; corollas salverform, lobes 5, shorter than tube; Florida only.	Voyria
2	Leaves and usually stems green; some leaf blades 5+ mm.	> 4
4	Flowers subtended by 2 separate, leaflike bracts but without calyx.	Obolaria
4	Flowers with calyx of 4–12(–14) sepals, some or all connate at least near base.	> 5
5	Corollas with projecting summits of plicae between lobes, or (in G. sceptrum) with the summit of the plicae forming a truncate gap between the lobes.	Gentiana
5	Corollas without plicae or truncate gaps between lobes.	> 6
6	Stigmas decurrent along sutures of ovary; corollas rotate to widely campanulate.	Lomatogonium
6	Stigmas not decurrent on ovary; corollas salverform, funnelform, campan­ulate, subrotate, or rotate.	> 7
7	Nectaries in pits prominent adaxially on corolla lobes, pit openings (and sometimes adjacent areas on corolla lobes) with fringed or pro­jecting margins.	> 8
8	Nectaries 1 per corolla lobe, or if 2 with both opening into single fringe-rimmed area on corolla lobe.	Frasera (in part)
8	Nectaries 2 per corolla lobe, with completely separate openings each surrounded by fringed rim.	> 9
9	Cauline leaves opposite or alternate; corollas blue or violet-blue (rarely greenish white), 4- or 5-lobed.	Swertia
9	Cauline leaves whorled; corollas yellowish green with purple spots and occasionally purple suffusion, 4-lobed.	Frasera (in part)
7	Nectaries, if present, not in pits with fringe-rimmed openings (corolla may be fringed at throat, but fringes do not surround nectary-pit openings).	> 10
10	Corollas rotate; styles cleft 1+ mm, style branches and stigmas often helically coiled; anthers coiling circinately or remaining nearly straight.	Sabatia
10	Corollas tubular, salverform, funnelform, or campanulate; styles not cleft or cleft to 1 mm, neither style branches nor stigmas coiling; anthers remaining straight or coiling helically.	> 11
11	Corollas widely campanulate, lobes 2+ times as long as tube.	Eustoma
11	Corollas funnelform or salverform, lobes shorter than 1.5 times tube.	> 12
12	Corollas with fringes of trichomes or fringed scales on adaxial surface near base of lobes; margins of lobes not fringed.	> 13
13	Pedicels longer than subtending internodes; nectaries 2 times as many as corolla lobes.	Comastoma
13	Pedicels mostly shorter than subtending internodes; nectaries same number as corolla lobes.	Gentianella (in part)
12	Corollas without fringes or scales on adaxial surface near base of lobes; margins of lobes fringed or not.	> 14
14	Corollas tubular, funnelform, or campanulate, or if ± salverform then with fringes or conspicuous teeth on margins of lobes, lobes not abruptly spreading horizontally at summit of tube, margins entire, dentate-serrate, or fringed.	> 15
15	Corolla lobe margins entire, corollas 0.4–3 cm, lobes 4 or 5, shorter than tube.	Gentianella (in part)
15	Corolla lobe margins dentate-serrate or fringed, corollas (1.2–)2–8 cm, lobes 4, ± as long as tube, or if shorter then with margins as above.	Gentianopsis
14	Corollas salverform, with lobes abruptly spreading ± horizontally at summit of slender tube (corollas often closing in specimen preparation), margins entire or minutely erose near apex only.	> 16
16	Corollas yellow; anthers remaining straight, not coiling.	Cicendia
16	Corollas pink to rose-violet or occasionally white; anthers coiling helically.	> 17
17	Inflorescences largely spicate, only proximally, if at all, dichasial.	Schenkia
17	Inflorescences dichasially or partly monochasially cymose (distally sometimes racemoid or subcapitate).	> 18
18	Stigmas 2, elliptic to ovate or orbiculate; capsules cylindric.	Centaurium
18	Stigmas 2, fan-shaped, or 1, 2-lobed (sometimes appearing sub­capitate in Zeltnera trichantha); capsules ovoid to ellipsoid.	> 19
19	Stigmas 2, fan-shaped, or 1, with 2 ± fan-shaped lobes.	Zeltnera
19	Stigma 1, shallowly 2-lobed with hemispherical lobes.	Gyrandra