Gentiana, Linnaeus, 1753

Wai, Jarearnsak Sae, 2024, Gentiana betongensis (Gentianaceae), a new species from tropical montane sphagnum bog in Peninsular Thailand, Phytotaxa 633 (1), pp. 60-67 : 65

Key to the species of Gentiana in Thailand, Peninsular Malaysia and Borneo

(modified from Ubolcholaket 1987)

1. Leaves closely arranged, small, resembling scales ................................................................................................... G. lycopodioides

- Leaves not as above............................................................................................................................................................................2

2. Calyx lobes obtuse........................................................................................................................................................... G. arenicola

- Calyx lobes acute or long acuminate to apiculate ..............................................................................................................................3

3. Calyx lobes irregular unequal, with 3 smaller linear and 2 larger foliaceous lobes............................................................. G. crassa

- Calyx lobes equal or subequal............................................................................................................................................................4

4. Calyx lobes shorter than the tube .......................................................................................................................................................5

- Calyx lobes as long as or longer than the tube .................................................................................................................................11

5. Flowers pedicellate....................................................................................................................................................... G. pedicellata

- Flower sessile or subsessile ................................................................................................................................................................6

6. Roots stout, fusiform-napiform, fleshy, 3–4 mm thick ................................................................................................ G. napulifera

- Root fibrous, slender ..........................................................................................................................................................................7

7. Calyx lobes with squarrose margin ................................................................................................................................. G. loureiroi

- Calyx lobes with entire margin...........................................................................................................................................................8

8. Flowers more than 2 cm long; calyx tube longer than 5 mm ............................................................................................ G. jarmilae

- Flowers less than 2 cm long; calyx tube shorter than 5 mm ..............................................................................................................9

9. Stems much-branched; corolla with bilobed plicae............................................................................................. ……. G. borneensis

- Stems simple or few-branched; corolla with unlobed plicae............................................................................................................10

10. Corolla lobes triangular-ovate with acute apex; stigma lobes recurved and coiled .................................................... G. betongensis

- Corolla lobes subspathulate with rounded apex; stigma lobes not coiled....................................................................... G. malayana

11. Stems indistinct when simple or distinct when branched; leaves basal rosette or scattered on the branches ...................................... .................................................................................................................................................... G. nudicaulis subsp. lakshnakarae

- Stems distinct, simple; leaves crowed at the top ..............................................................................................................................12

12. Corolla with acute plicae; disk present.......................................................................................................................... G. hesseliana

- Corolla with bifid plicae; disk absent .................................................................................................................................. G. timida