Gentiana

Herbs annual, biennial, or perennial, chlorophyllous, glabrous or stems and calyces puberulent; stems solitary or clustered from a single crown, arising at intervals from a horizontal rhizome only in G. glauca. Leaves cauline, opposite [whorled], sometimes also basal. Inflorescences terminal and sometimes axillary cymes, often condensed into heads, or flowers solitary; terminal heads or dense cymes usually subtended by 1–3 pairs of involucral leaves; in species of sect. Pneumonanthe (specified in discussion below) that generally have flowers in dense heads or cymes, the flowers are individually subtended by paired small bracts (some bracts may be absent when flowers are in dense, many-flowered heads), bracts absent in G. autumnalis and G. pennelliana. Flowers usually 5-merous, sometimes 4-merous (G. prostrata) [G. cruciata], rarely to 7-merous; calyx tube cylindric to narrowly campanulate or less often cleft and spathaceous (only in G. platypetala, occasionally in G. affinis), calyx tube (except G. fremontii and G. prostrata) extending above bases of the lobes, which thus appear to diverge below the summit, calyx lobes ascending to nearly erect (except G. clausa, G. flavida, and G. latidens, in which they spread nearly horizontally); corolla blue, greenish blue, violet, rose-violet, pale yellow, greenish yellow, or white [deeper yellow, orange, red], campanulate, funnelform, tubular, or salverform, gla­brous within, lobes shorter than tube, margins entire or minutely erose-serrate, alternating with projecting or rarely truncate plicae (defined below), spurs absent; stamens inserted in proximal 1/2 of corolla tube; anthers distinct or connate; ovary stipitate; style persistent, erect, short or not clearly differentiated from ovary; stigmas 2; nectaries as many as corolla lobes, on gyno­phore. Capsules ovoid-ellipsoid to cylindric (short-obovoid in G. fremontii), dorsiventrally compressed, stipitate. x = 6, 7, 9, [10], 13.

Distribution

North America, Mexico, Central America, South America, Eurasia, nw Africa, Atlantic Islands (Iceland), sw Pacific Islands, Australia.

Discussion

Species ca. 400 (28 in the flora).

Gentiana nivalis is in sect. Calathianae Froelich. Gentiana glauca is in sect. Kudoa (Masamune) Sataka & Toyokuni. Gentiana algida is in sect. Frigida Kusnezow. Species 4 through 25, plus G. septemfida Pallas, are in sect. Pneumonanthe Gaudin. Species 26 through 28 are in sect. Chondrophyllae Bunge. Gentiana lutea Linnaeus is in sect. Gentiana, and G. cruciata Linnaeus is in sect. Cruciata Gaudin (A. Favre et al. 2016).

In most of the perennial species, flowering stems arise directly from the caudex, with the basal and near-basal leaves reduced and scalelike, the cauline leaves gradually increasing in size distally. Gentiana algida, G. newberryi, and G. setigera non-flowering stems, with the leaves generally so closely spaced as to form rosettes, arise from the caudex, and flowering stems, the following year, although they may appear to arise from the caudex, arise from axillary buds of the previous year’s rosettes. The proximal cauline leaves, rather than being reduced, are as large as or larger than the distal leaves.

Except in Gentiana lutea, the primary components of the corolla tube in Gentiana alternate with distally widening, and in most sections, more or less infolded components of similar tex­ture, which are vascularized only by branches from the lateral veins of the adjacent petals on each side. In most species, these extend into free portions, which alternate with the corolla lobes. These components of the corolla, historically called appendages, are now generally called plicae. (In G. nivalis, the plicae may be infolded so that the free portions appear superficially to adaxially at the base of the lobes rather than between them.) In nearly all of the species in the flora area, the sinuses on each side of each plica are equally deep or nearly so. Only in G. flavida, G. linearis, and G. villosa are these sinuses distinctly unequal, the sinus nearer the apex of the obliquely triangular free portions of the plicae being conspicuously less deep than the other. The free portions of the plicae are generally more or less erect, except that in G. decora the smaller of the two divisions, to the left as viewed adaxially, is often inflexed. The form of the free portions of the plicae is very useful in distinguishing among some of the species in the flora area. Herbarium specimens should be prepared so that these floral parts are visible, preferably by including a corolla slit lengthwise and unrolled.

In most of the species of sect. Pneumonanthe in the flora area, the exceptions being Gentiana villosa in the East and G. calycosa and G. parryi in the West, the distal cell-wall corners of the marginal leaf cells extend outward into cilia (seen at 10×). In the exceptions, the cell-wall corners extend outward only far enough to appear as minute teeth.

In all species except those in sect. Chondrophyllae, the calyx tube extends above the bases of the lobes, so that the lobes appear to diverge from the abaxial surface slightly below the truncate summit, with gaps between the bases of the lobes. This intracalycular membrane is interpreted as an invagination of the adaxial surface. In sect. Chondrophyllae, the calyx lobes diverge at the summit of the tube, with only V- or U-shaped sinuses between them, although in Gentiana fremontii, in sect. Chondrophyllae, the longitudinal infolding of the hyaline portions of the tube below the sinuses may give the appearance of an intracalycular membrane.

In Gentiana, as in some other Gentianaceae, some species have corollas that open only in sunshine; in some other Gentiana species, the corollas remain essentially closed. In species with corollas that open, the portions of the corolla lobes exposed in bud and the tube below each lobe are often suffused abaxially with green and/or purple. In species 4 through 24, relatively dark continuous or fragmented stripes commonly extend downward adaxially between the central and lateral veins of each petal into the paler proximal portion of the tube, and their presence does not serve to distinguish among species. The gynophores elongate as the fruits mature, variably so even within a species. Elongation is often especially prominent in Gentiana glauca, G. newberryi, and G. prostrata, elevating all or much of the capsule above the persistent corolla.

In some species in sect. Pneumonanthe, the distal corners of the marginal cell walls of the leaves and calyx lobes are prolonged to the extent that they appear as short, firm cilia when seen at 10×; in other species they are shorter, merely forming minute teeth. The presence or absence of such cilia is useful in identifying small or otherwise exceptional specimens of some species, especially in the Coast Ranges and the Rocky Mountains.

In those species in sect. Pneumonanthe in which most or all of the flowers are clustered in a terminal head, this terminal inflorescence is directly subtended by leaves, usually in two or three densely spaced pairs, that are about as large as the distal cauline leaves and of the same color, texture, and, in most species, shape. These are called “involucral leaves” here. The term “bracts” is used here for much smaller structures, mostly less than 2 cm, that directly subtend the individual flowers. These bracts are usually paired, but in large inflorescences, their develop­ment may be somewhat irregular.

Species in sect. Pneumonanthe are extensively interfertile, with at least 18 interspecific hybrid combinations known to have occurred in nature (J. S. Pringle 1967; studies for this flora). These species, all of which have 2n = 13, are relatively large-flowered and are pollinated primarily by bumblebees. The hybrids, which are fertile, represent occasional events involving otherwise well-differentiated species that are usually more or less isolated geographically and/or ecologically and in some cases are highly dissimilar in floral morphology. Hybrids are most frequent among the prairie species Gentiana andrewsii, G. flavida, and G. puberulenta.

Gentiana lutea, great yellow gentian, native to Europe, is adventive in Alberta. Plants of this species are 0.5–2 m tall, with solitary, stout, unbranched stems and widely ovate to elliptic leaves to 30 cm. The flowers are borne in dense, terminal and axillary clusters and have bright yellow, deeply cleft corollas 10–25 mm, with five (to nine) spreading, linear lobes. As noted above, G. lutea lacks the plicae between the corolla lobes that are otherwise characteristic of the genus. Gentiana cruciata, crosswort or star gentian, also native to Europe, has escaped from cultivation in Manitoba and Massachusetts. It has a basal rosette of strap-shaped leaves, decumbent stems with numerous ovate-elliptic leaves, and flowers in small axillary and terminal clusters. The mostly four-lobed corollas are bright blue, 20–25 mm, with spreading lobes alternating with small, nearly symmetrically triangular or few-toothed plicae. Gentiana septemfida in the narrow sense, crested gentian or summer gentian, native to the Caucasus Mountains of Eurasia, has escaped in Ontario, Illinois, and Wisconsin. It resembles G. plurisetosa but has more numerous, lance-ovate leaves and usually more flowers per stem, in a terminal cluster. The corollas are deep blue, 30–50 mm, with spreading lobes and prominent, finely divided free portions of the plicae.

In addition to those mentioned above, some other European and Asiatic species of Gentiana are grown as ornamentals in North American gardens, although none has become really com­mon in cultivation. Several species in sect. Ciminalis (Adanson) Dumortier and sect. Kudoa are cultivated in alpine gardens in the cooler parts of the flora area, and other species, mostly in sect. Cruciata and sect. Pneumonanthe, are cultivated in perennial borders.

Selected References

None.

Lower Taxa

Gentiana affinis, Gentiana algida, Gentiana andrewsii, Gentiana austromontana, Gentiana autumnalis, Gentiana calycosa, Gentiana catesbaei, Gentiana clausa, Gentiana decora, Gentiana douglasiana, Gentiana flavida, Gentiana fremontii, Gentiana glauca, Gentiana latidens, Gentiana linearis, Gentiana newberryi, Gentiana nivalis, Gentiana parryi, Gentiana pennelliana, Gentiana platypetala, Gentiana plurisetosa, Gentiana prostrata, Gentiana puberulenta, Gentiana rubricaulis, Gentiana saponaria, Gentiana sceptrum, Gentiana setigera, Gentiana villosa

Key

1	Plants 0.1–2.5(–3) dm; corollas 7–25 mm; subarctic to arctic and/or subalpine to alpine regions.	> 2
2	Flowers solitary or in dense terminal heads of 2–5(–7); calyx tube extending adaxially above base of lobes.	> 3
3	Annuals, with a single flowering stem; rhizomes absent; corollas salverform, with spreading lobes, deep blue or rarely white.	Gentiana nivalis
3	Perennials, with flowering stems arising at intervals from horizontal rhizomes; corollas tubular, with ascending lobes, greenish blue, greenish yellow, or rarely white.	Gentiana glauca
2	Flowers solitary on an unbranched stem or at ends of branches, in the latter case the inflorescence forming a diffuse cyme; calyx tube not extending above base of lobes.	> 4
4	Flowers in a diffuse cyme; corollas predominantly white, adaxially with purple dots; free portions of corolla plicae divided to base into 2 equal segments.	Gentiana douglasiana
4	Flowers solitary; corollas white or blue, without adaxial dots; free portions of corolla plicae triangular, merely erose or at most shallowly notched.	> 5
5	Leaf blades obscurely or not white-margined; all cauline leaves ± spreading; corollas adaxially medium to deep blue or occasionally white; capsules compressed-cylindric.	Gentiana prostrata
5	Leaf blades conspicuously white-margined; distal cauline leaves strongly ascending; corollas adaxially white or pale (rarely deeper) blue; capsules short-obovoid.	Gentiana fremontii
1	Plants (0.1–)0.4–12 dm; corollas (12–)18–65 mm (if plants less than 2.5 dm, corollas more than 23 mm); species widely distributed.	> 6
6	Calyx tubes deeply cleft into 2 spathaceous segments, calyx lobes minute; corolla lobes 6–11 mm; free portions of corolla plicae low-triangular, less than 1 mm, merely notched, otherwise entire.	Gentiana platypetala
6	Calyx tubes not deeply cleft, with well-developed lobes, or occasionally cleft with some lobes much reduced in G. affinis, in which the free portions of the corolla plicae are larger and laciniate.	> 7
7	Flowers usually solitary on unbranched stems, occasionally on stems with 1 or 2 branches each bearing a solitary flower; peduncles (0.3–)1–8 cm, with neither invo­lucral leaves nor bracts at base of flowers; corollas 30–65 mm, open, with spread­ing lobes; corolla lobes 10–25 mm; species of Atlantic and Gulf coastal plains.	> 8
8	Corollas usually blue, rarely rose-violet or white; Atlantic Coastal Plain, New Jersey to South Carolina.	Gentiana autumnalis
8	Corollas white, abaxially suffused with purplish green on and below lobes; nw Florida.	Gentiana pennelliana
7	Flowers usually in terminal heads or compact cymes of 2–25, rarely solitary, some­times also in distal axils of primary stem or on short lateral branches, sessile above paired bracts; corollas (12–)18–60 mm, opening or remaining closed; corolla lobes 0.5–17 mm; species widely distributed, in diverse habitats.	> 9
9	Non-flowering rosettes of leaves present at flowering time; flowering stems arising laterally below summit of a rosette, and/or basal and near-basal leaves of flowering stems, densely spaced, persistent; at least some rosette or basal leaves 2–14 cm, larger than distal leaves.	> 10
10	Free portions of corolla plicae divided nearly to base into 2 or 3 threadlike parts.	Gentiana setigera
10	Free portions of corolla plicae less deeply or finely divided, segments threadlike only toward apex if at all.	> 11
11	Corolla lobes ascending; plicae erose, not cleft into triangular segments; rosette and basal leaf blades narrowly spatulate to oblanceolate, 6+ times as long as wide.	Gentiana algida
11	Corolla lobes spreading; plicae ± bifid, with 2 triangular, serrate to lacerate segments; rosette and basal leaf blades widely spatulate to obovate or oblanceolate, less than 6 times as long as wide.	Gentiana newberryi
9	Non-flowering rosettes absent at flowering time, flowering stems arising directly from cau­dex; basal and lowest cauline leaves reduced, ± scalelike.	> 12
12	Corollas remaining tightly closed; corolla lobes reduced to a mucro or 0.5–2(–3) mm, distinctly shorter than plicae.	Gentiana andrewsii
12	Corollas remaining closed or opening; corolla lobes 0.7–15 mm, ± as long as or longer than plicae.	> 13
13	Corolla plicae truncate and entire at the summit, not or scarcely extending above base of lobes.	Gentiana sceptrum
13	Corolla plicae triangular to ± oblong, bifid, toothed, or fimbriate at the summit, with free portions extending above base of lobes.	> 14
14	Free portions of corolla plicae divided nearly to base into a fringe of 5–20 threadlike parts.	Gentiana plurisetosa
14	Free portions of corolla plicae not or less deeply or finely divided, segments threadlike only toward apex if at all.	> 15
15	Free portions of corolla plicae obliquely triangular, that is, confluent with the adjacent lobe higher on the left side when the adaxial surface is viewed, wider than long, sometimes with a few low teeth but not cleft or lacerate.	> 16
16	Distal leaf blades linear to lanceolate, generally less than 15 mm wide and 6+ times as long as wide.	Gentiana linearis
16	Distal leaf blades lanceolate to ovate, elliptic, obovate, or spatulate, 15+ mm wide and/or less than 6 times as long as wide.	> 17
17	Calyx lobes lanceolate to ovate-triangular, spreading; corollas white, sometimes tinged pale yellow.	Gentiana flavida
17	Calyx lobes linear to oblong-lanceolate or oblanceolate, ascending; corollas usually violet-blue, violet, or greenish white ± suffused with violet, occasionally rose-violet or white.	> 18
18	Involucral leaves ascending and proximally conduplicate, ± enveloping base of inflorescence; proximal and mid-stem leaf blades linear to oblong or ovate.	Gentiana rubricaulis
18	Involucral leaves spreading, not enveloping base of inflo­rescence; proximal and often mid-stem leaf blades elliptic or obovate to spatulate.	Gentiana villosa
15	Free portions of corolla plicae shallowly to deeply bifid, with the summit distinctly erose, toothed, or lacerate, not oblique, that is, with the sinuses on each side of a plica not distinctly unequal.	> 19
19	Leaf blades widely ovate to orbiculate, mostly less than 2 times as long as wide; marginal leaf and calyx-lobe cell walls forming minute teeth (seen at 10×) but not extending into cilia; corollas open; seeds not winged.	> 20
20	Involucral leaves similar to or smaller than distal cauline leaves, ± spreading from the base, not enveloping bases of inflorescences.	Gentiana calycosa
20	Involucral leaves wider than distal cauline leaves, proximally con­duplicate, ascending and enveloping bases of inflorescences.	Gentiana parryi
19	Leaf blades linear, oblong-lanceolate, or lanceolate to elliptic or ovate, generally 2+ times as long as wide (rarely proportionately shorter in G. catesbaei); marginal leaf and calyx-lobe cell walls extending into cilia (seen at 10×); corollas opening or remaining closed; seeds winged.	> 21
21	Corollas tubular-funnelform to narrowly campanulate, opening with spreading or reflexed lobes.	> 22
22	Corollas (12–)18–40(–45) mm, lobes 3–7(–10) mm, less than 2 times as long as free portions of plicae.	Gentiana affinis
22	Corollas (30–)35–60 mm, lobes 6–15 mm, 2+ times as long as free portions of plicae.	Gentiana puberulenta
21	Corollas tubular, opening to various degrees or remaining closed.	> 23
23	Corolla lobes 0.7–3 mm, ± as long as plicae, if lobes 2+ mm (G. austromontana), then lobes ca. 1/2 as wide as free portions of plicae; corollas remaining completely closed.	> 24
24	Corolla lobes ca. as wide as free portions of plicae; calyx lobes widely elliptic to obovate or orbiculate; stems and calyx tubes glabrous.	Gentiana clausa
24	Corolla lobes ca. 1/2 as wide as free portions of plicae; calyx lobes lanceolate to narrowly ovate or elliptic; stems and calyx tubes puberulent.	Gentiana austromontana
23	Corolla lobes 2.5–10 mm, in most species exceeding plicae, if lobes less than 3 mm or ± as long as plicae (G. latidens), then lobes ca. as wide as free portions of plicae; corollas remaining loosely closed or slightly to widely opening.	> 25
25	Calyx lobes spreading nearly horizontally when fresh, mostly ovate, obovate, orbiculate, or rhombic; corolla plicae ± as long as lobes; mountains of w North Carolina.	Gentiana latidens
25	Calyx lobes ± erect, linear-subulate, lanceolate, elliptic, or oblanceolate; corolla plicae shorter than lobes; more widely distributed in e, c United States.	> 26
26	Calyx lobes subulate to linear or rarely oblanceolate; calyx tubes and stems puberulent; corolla plicae unequally bifid at summit, narrower segment usually deflexed.	Gentiana decora
26	Calyx lobes narrowly elliptic to oblanceolate; calyx tubes glabrous, stems glabrous or occasionally ± puberulent; corolla plicae subequally bifid at summit, both segments erect.	> 27
27	Leaf blades linear to elliptic, widest near middle; calyx lobes shorter than or ± as long as tube; corolla lobes usually less than 2 mm longer than plicae; widely distributed in e, c United States.	Gentiana saponaria
27	Leaf blades usually ovate, widest near base; calyx lobes mostly longer than tube; corolla lobes usually 2–4 mm longer than plicae; Atlantic Coastal Plain.	Gentiana catesbaei