trees: e.g., Anthocleista, Chorisepalum, Fagraea, Macrocarpaea, Potalia, Prepusa, Symbolanthus

shrubs: e.g., Adenolisianthus, Chorisepalum, Gentianothamnus, Fagraea, Ixanthus, Macrocarpaea, Orphium, Potalia, Prepusa, Saccifolium, Symbolanthus, Tachia

woody lianas and climbers: e.g., Anthocleista spp., Lagenanthus, Purdieanthus

herbaceous climbers: e.g., Bisgoeppertia, Crawfurdia

herbs: most gentians

single-stemmed trees and shrubs (monocarpic): Potalia

candelabra-shaped branching: Anthocleista spp.

leaves crowded at branch apices: many in subtribe Potaliinae and tribe Helieae

autotrophic plants: most gentians

heterotrophic plants, mycotrophs, saprophytes: Bartonia (partly heterotrophic), Cotylanthera, Obolaria (partly heterotrophic), Sebaea oligantha, Voyria, Voyriella

dioecious plants (male and female flowers on separate plants): Gentianella spp., Veratrilla. All other gentians have flowers that have fully functional male (stamens) and female (gynoecium) parts in the same flower.

prostrate habit (horizontal branching on the ground, rooting at the nodes): Exacum spp.

taproots: most gentians

coralloid roots, bird's nest roots (associated with mycorrhiza): Obolaria, Voyria, Voyriella

glabrous plants (lacking hairs): most gentians

hairy plants: Chironia spp., Macrocarpaea spp., Microrphium, Ornichia, Orphium

glandular hairs:

glaucous plants (with a waxy, bluegreen surface layer): Blackstonia, Eustoma

viscid plants (sticky): Ixanthus

bristles on vegetative parts (hard, sharp hairs): Microrphium, Orphium

corky bark: Saccifolium

hollow stems: common

terete (round) stems: common

quadrangular (4-cornered) stems: common

winged stems: common

opposite leaves (leaves 2 and 2 along stem): nearly all gentians

alternate leaves (leaves single along stem): Saccifolium, Voyriella spp.

whorled leaves (verticillate, 3 or more together along stem): Curtia spp., Exacum spp.

leaves in basal rosette (rosulate): many gentians, especially in Chironieae and Gentianeae, e.g., Centaurium spp., Gentianella spp.

amplexicaul/perfoliate leaves (opposite leaves that are fused together at their bases): Exacum spp., Prepusa spp., Symphyllophyton, Tachiadenus spp.

saccate leaves (sack-shaped): Saccifolium

entire leaves (margin smooth, not lobed or dissected): all gentians (except Irlbachia poeppigii and some Fagraea)

dentate leaves (margin with teeth): Fagraea spp., Irlbachia poeppigii

scale-like leaves (leaves very small, like scales): Bartonia, Cotylanthera, Sebaea oligantha, Voyria, and Voyriella

interpetiolar line (ridge between the base of a pair of leaves): most gentians

interpetiolar stipules (a flap of leaf-like tisse between a pair of leaves): Macrocarpaea spp., very rare in the family, only occurs in one species

interpetiolar sheath ( a ring of tissue around the stem at the base of a pair of leaves): Anthocleista, Chorisepalum, Fagraea, Lisianthius, Macrocarpaea, Potalia 

auricules at base of leaves (ear-shaped appendages at the base of a leaf): Anthocleista spp., Fagraea spp.

axillary spines (spines in the leaf axil): Anthocleista

acrodromous leaf venation (arcuate, few veins, bent towards apex of leaf): common

brochidromous leaf venation (pinnate, veins straight towards edge of leaf): common in some genera, e.g., Anthocleista, Macrocarpaea spp., Fagraea, 

axillary inflorescences (in leaf axils): many gentians, e.g.,  Enicostema, Saccifolium, Tachia, Zonanthus

terminal inflorescences (at top of branch): many gentians

solitary flowers (flowers one by one, not together): Cotylanthera, Gentianothamnus, Saccifolium

cymes (a type of inflorescence with a top flower and side branches that repetitive branch sideways, symmetrically or assymmetrically): most gentians

racemes: Fagraea spp.

capitate (flowers in tight heads): Cracosna, Tapeinostemon spp.

spicate (flowers in a spike): Coutoubea

cymes with monochasial branches (branches that only branch on one side, giving the appearance of one long branch with many flowers on one side): Chelonanthus, Irlbachia, Symbolanthus

flowers sessile (flowers without flower stalk, sitting directly on stem): Tachia, Tapeinostemon sessiliflorum, many in subtribe Faroinae

bracts and bracteoles scale-like, small (bracts are the small leaves in the inflorescence, often occur in pairs): most gentians

bracts leaf-like: Macrocarpaea

bracts perfoliate (a pair of bracts that are fused together at their base) : Ixanthus

extra bracts (more than 2) below flower or inflorescence: Fagraea spp.

3-merous flowers (3 calyx lobes, 3 corolla lobes, 3 stamens): Pycnosphaera (rarely in Enicostema)

4-merous flowers: many gentians, e.g., Canscora, Centaurium spp., Cicendia, Congolanthus, Coutoubea, Cracosna, Djaloniella, Exaculum, Faroa, Geniostemon, Hoppea, Ixanthus [also 5-merous], Karina, Neurotheca, Oreonesion, Sabatia spp., Schinziella (rarely in Enicostema)

5-merous flowers: most gentians

6-merous corolla: Chorisepalum, Blackstonia spp., Prepusa, Senaea (occasionally 6-7 also in some other genera: Enicostema, Gentiana, Irlbachia).

8-16-merous corolla and stamens: Anthocleista (10-16), Blackstonia (6-12), Potalia (8-10), Sabatia (4-5, 8-13), Urogentias (8)

2 sepals, 4 petals, 4 stamens: Cracosna, Obolaria

2 sepal lobes, 5 petals, 5 stamens: Microrphium

3 sepals, 4 petals, 4 stamens: Cracosna

4 sepals, 6 petals, 6 stamens: Chorisepalum

4 sepals, 8-16 petals, 8-16 stamens: Anthocleista, Potalia

hypogynous (ovary superior): all gentians

unisexual flowers: Veratrilla and Gentianella spp.

heterostylous flowers: only in tribe Saccifolieae, e.g., Curtia, Hockinia, Tapeinostemon spp., Voyriella [Knoblauch, 1895]

cleistogamous: Sebaea oligantha only

actinomorphic (radially symmetric) flowers: most gentians

nodding flowers (hanging down): Crawfurdia, Lagenanthus, Lehmanniella, Lisianthius, Purdieanthus

fused sepals (at least at base of calyx): most gentians

free sepals: Anthocleista, Chorisepalum, Potalia

actinomorphic (symmetrical) calyx: most gentians

zygomorphic (bilateral) calyx: Exacum spp., Frasera

wing (lower picture) or keel (upper picture) on back of sepals: Canscora spp., Cicendia, Exacum spp., Schultesia spp., Symbolanthus spp., Tachia spp., Tachiadenus spp.
Wings are very thin; keels are thicker at the base.

dorsally thickened sepals: many in tribe Helieae, many also have wings or keels

membranaceous sepals (paper-thin): Prepusa

sepals deciduous (fall off) in fruiting stage: Chorisepalum, Macrocarpaea, Tachia

yellow-orange calyx: Potalia

imbricate calyx lobes in bud: common

decussate calyx lobes in bud: Anthocleista, Chorisepalum, Potalia

membrane between calyx lobes (intracalycine membrane: Crawfurdia spp., Gentiana spp.

fused petals (sympetaly): all gentians  are at least fused at the very base of the petals

actinomorphic corollas (symmetric, all lobes equal): most gentians

slightly zygomorphic corollas (not symmetric, lobes unequal) : e.g., Canscora spp., Chelonanthus spp., Symbolanthus spp.

rotate corollas (deeply divided, only fused at base, lobes spreading widely): e.g., Frasera, Swertia

tubular corollas (straight tube, lobes straight): e.g., Potalia spp.

salvershaped corollas (like a trumpet, narrow tube and flaring lobes): e.g., Lisianthius spp., Symbolanthus spp., Tachia spp., Tachiadenus

funnelshaped corollas (like a funnel, narrow tube and lobes spreading, but not flaring): e.g., Chelonanthus, Gentianothamnus, Symbolanthus spp., Tetrapollinia

bellshaped corollas (campanulate):

contort corolla lobes in bud (all lobes twisted and overlapping in bud): most gentians

imbricate corolla lobes in bud (lobes overlapping except two, one inner and one outer): Bartonia, Obolaria, Saccifolium only

valvate+contort corolla lobes in bud (valvate = lobes not overlapping, only sitting edge to edge): Aripuana only

petal edges erose (papillate): common in many genera

petal edges ciliate or dentate (with hairs or teeth along edge): Gentianopsis, Pterygocalyx

fimbriae (hairs) at the base of the corolla lobes: Comastoma, Gentiana, Gentianella spp.

folds (plicae) between corolla lobes (thinner folded tissue fusing corolla lobes): Crawfurdia, Gentiana spp., Metagentiana, Tripterospermum

each petal with a spur (a thin, long and hollow structure attached to a petal): Halenia only

white petals: e.g., Anthocleista, Coutoubea, Enicostema, Irlbachia spp., Fagraea spp., Saccifolium, Symbolanthus spp., Tachiadenus spp.

yellow petals: e.g., Blackstonia spp., Ixanthus spp., Sebaea spp., 

orange petals: e.g., Lagenanthus spp., Tapeinostemon spp., 

red petals: e.g., Gentianella spp., Rogersonanthus spp., Symbolanthus spp.

pink petals: e.g., Centaurium spp., Sabatia, Symbolanthus spp.

purple petals: e.g., Anthocleista spp., Chelonanthus spp., Exacum spp., Gentianella spp., Halenia spp.

blue petals: e.g., Exacum spp., Gentiana spp.

black petals: Lisianthius nigrescens

green petals: e.g., Chelonanthus spp., Macrocarpaea spp., Potalia spp.

petals with nectar guides (stripes inside corolla mouth and/or on lobes): Symbolanthus spp.

corolla with lighter-colored 'eye' in middle of flower: Eustoma, Sabatia

corolla persistent in fruit (does not fall off when fruits develop): many Gentianeae and Chironieae

colleters (small, finger-shaped glands on inside of sepals): common in many gentians and other families of the Gentianales

colleters absent from calyx: e.g., Bisgoeppertia, Coutoubea, Cracosna, Eustoma

glandular ridge on back of sepals: common in Helieae

nectaries on inside of corolla tube or on lobes: Frasera spp., Gentianella spp., Swertia spp., 

nectary disk at base of ovary: many in tribes Potalieae and Helieae, a few in subtribe Gentianinae, e.g., Gentianothamnus, Tripterospermum

glands at apex of anther: Sebaea spp.

glands at base of anther: Sebaea spp.

stamens fewer than corolla lobes: Canscora spp., Hoppea, Schinziella

stamens alternating with corolla lobes: all gentians

stamens inserted in the corolla tube: most gentians

stamens inserted in the corolla lobe sinuses: e.g., Aripuana, Djaloniella, Faroa, Geniostemon, Sabatia, Swertia spp.

actinomorphic stamens (symmetric): most gentians

zygomorphic stamens (assymmetric) : e.g., Calolisianthus, Chelonanthus, Cotylanthera, Exacum spp., Orphium, and Symbolanthus

anisomorphic stamens (stamens of different shapes and sizes): Canscora, Hoppea, Schinziella

corona at the base of stamens (ring of tissue): Symbolanthus only

appendages at base of stamens (flaps, hoods, wings): common in subtribe Faroinae and Coutoubea

flattened filaments: many in tribe Saccifolieae

curved filaments: Gentiana sect. Stenogyne and Tripterospermum

winged filaments: Gentiana spp.

apically recurved filaments (filament strongly turned close to the anther): many in tribe Helieae

fused (partially or completely) filaments: Anthocleista, Potalia

fused (connate) anthers: Gentiana spp., Sebaea spp., Tachiadenus spp. [Duncan & Brown, 1954]

long, linear anthers: e.g., Anthocleista, Deianira, Fagraea spp., Potalia, and many in tribe Helieae

recurved (bent) anthers: many in tribe Helieae, e.g., Chelonanthus, Symbolanthus

spirally twisted/coiled anthers: many in subtribe Chironiinae, e.g., Centaurium, Chironia, Orphium, Sabatia, Canscora

twisted backwards anthers: Sebaea spp.

longitudinally dehiscent anthers  (with slits): most gentians

poricidal anthers (pores at apex): Cotylanthera (1 pore), Exacum spp. (2 pores)

introrse anthers (open toward the middle of flower, on the inside of the anther): most gentians

latrorse anthers (open toward the sides of the anthers): Voyriella spp., Saccifolium

anthers with apical appendages (with extra tissue on the tip of the anther): many in tribes Exaceae, Helieae, and Saccifolieae

anthers with basal appendages: some in tribe Exaceae

coriaceous anthers (leathery, thick anthers): Exacum, Gentianothamnus

bicarpellate gynoecium (formed from 2 fused carpels): all gentians

syncarpous gynoecium: all gentians

stipitate gynoecium (on gynophore): many in tribe Gentianeae

sessile gynoecium: most gentians

style long, filiform, distinct: many in tribes Exaceae, Helieae, Potalieae

style twisted when dry: many Helieae

style zygomorphic: many in tribe Exaceae and Helieae

style short or absent: many in tribe Gentianeae

decurrent stigma along carpel sutures: Bartonia, Lomatogonium spp.

with additional lower stigma: Sebaea spp. [Marloth, 1909]

strongly bilamellate (bilobed) stigma: many Helieae, Fagraea spp., Centaurium, Eustoma

capitate stigma: common, e.g., Lisianthius, Potalia

simple stigma: common in tribe Exaceae

peltate stigma: Voyria spp.

long, coiling stigmatic lobes: Sabatia

capsules, dry and thin: most gentians

capsules, leathery: Symbolanthus

capsules, woody: Chorisepalum, Tachia

berries: Anthocleista, Chironia baccifera, Fagraea, Potalia, Tripterospermum spp.

(many different colors)

apical, septicidal dehiscence (opens from top along sutures): most gentians with capsules

apical dehiscence, with coriaceous lid: Exacum spp.

medial dehiscence (opens in the middle): some Helieae, Voyria spp.

capsule splits into 4 valves: Macrocarpaea spp., Chorisepalum

indehiscent fruits (never opens): Symbolanthus spp.?, Voyria spp.?, and the genera with berries

parietal placentation (placenta attached to fruit wall): many gentians (this character is very plastic and both parietal and axile placentation can be found within the same gynoecium/fruit in some species)

axile placentation (placenta attached to fruit center), at least for 1/2 of the length of the fruit: many in tribe Exaceae, some in Helieae

intruding placentas (placenta large and intruding far into the fruit from the walls and/or center): common in many gentians, especially in tribe Helieae, e.g., Anthocleista, Centaurium, Fagraea, Gentianothamnus, Tachiadenus

seeds distributed over entire inner wall of fruit: many in subtribe Swertiinae

numerous seeds: most gentians

round or oblong seeds: Tachia spp., Tachiadenus spp., Voyria spp.

flattened seeds: many in tribe Gentianeae, in subtribe Potaliinae, Chorisepalum, Macrocarpaea spp.

cup-shaped seeds: Exacum spp., Voyria spp.

winged seeds: some in tribe Gentianeae, Chorisepalum, Macrocarpaea spp.

angular seeds: common in tribes Exaceae and Helieae

filiform seeds: Voyria spp.

dust seeds (very small): Voyria

aril: absent in all gentians

aborted seeds, filiform: Voyria spp.