Revisiting the taxonomy of Exacum courtallense (Gentianaceae) and recognizing E. courtallense var. laxiflorum at the species rank Author Geethakumary, M. P. 0000-0002-2136-5987 Plant Systematic and Evolutionary Science Division, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Karimancode P. O., Thiruvananthapuram, Kerala 695562, India & geethatbgt @ gmail. com; https: // orcid. org / 0000 - 0002 - 2136 - 5987 geethatbgt@gmail.com Author Deepu, S. Plant Systematic and Evolutionary Science Division, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Karimancode P. O., Thiruvananthapuram, Kerala 695562, India & Forest Ecology Department, Kerala Forest Research Institute, Thrissur, Kerala 680653, India Author Kissling, J. 0000-0002-1078-4000 Institute of biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland & jonathan. kissling @ unine. ch; https: // orcid. org / 0000 - 0002 - 1078 - 4000 jonathan.kissling@unine.ch Author Pandurangan, A. G. Plant Systematic and Evolutionary Science Division, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Karimancode P. O., Thiruvananthapuram, Kerala 695562, India & Centre for Innovation in Science and Social Action, Thiruvananthapuram, Kerala 695010, India text Phytotaxa 2022 2022-08-23 559 2 185 192 journal article 132960 10.11646/phytotaxa.559.2.7 8d205305-4c48-47dd-9d00-3d1b0b660aa1 1179-3163 7021601 Key to Exacum species in the Western Ghats 1. Flowers 4-merous ...............................................................................................................................................................................2 - Flowers 5-merous ...............................................................................................................................................................................8 2. Calyx lobes without wings .................................................................................................................................................................3 - Calyx lobes with prominent wings .....................................................................................................................................................4 3. Flowers subsessile; calyx wings without prominent veins................................................................ E. sessile Linnaeus (1753: 112) - Flowers pedicellate; calyx wings with prominent veins................................................................... E. lawii C.B. Clarke (1885: 98) 4. Leaves 3-veined (midvein with one secondary vein on each side) ...................................... E. pedunculatum Linnaeus (1753: 112) - Leaves 5-veined (midvein with two secondary veins on each side) ..................................................................................................5 5. Anthers oblong ...................................................................................................................................................................................6 - Anthers linear .....................................................................................................................................................................................7 6. Leaves with a distinct petiole; calyx wings truncate ...................................................................... E. petiolare Grisebach (1845: 46) - Leaves sessile; calyx wings cordate .............................................................................................. E. pumilum Grisebach (1845: 46) 7. Calyx lobes cuspidate with broad rounded dorsal wing; anthers curved ................................ E. tetragonum Roxburgh (1832: 398) - Calyx lobes acuminate with a narrow dorsal wing; anthers straight ............................................ E. grande Klackenberg (1985: 43) 8. Dorsal side of the anther with a papilla present near the apex ...........................................................................................................9 - Dorsal side of the anther without a papilla.......................................................................................................................................14 9. Leaves petiolate or ± sessile.............................................................................................................................................................10 - Leaves amplexicaul or semiamplexicaul..........................................................................................................................................12 10. Perennial herbs; anthers oblong............................................................................ E. idukkianum Geethakumary et al. (2016a: 226) - Annual herbs; anthers linear.............................................................................................................................................................11 11. Stem 4-angled, winged; fruiting pedicel drooping....................................................................... E. wightianum Arnott (1839: 176) - Stem 4-lineolate, not winged; fruiting pedicel not drooping.................................................. E. klackenbergii Gopalan (2002: 271) 12. Style shorter than anthers ......................................................................................... E. keralense Geethakumary et al. (2016b: 429) - Style longer than anther....................................................................................................................................................................13 13. Leaves ovate, papilla in the dorsal side of anther distinct.................................................... E. atropurpureum Beddome (1874: 24) - Leaves elliptic, papilla in the dorsal side of anther indistinct ............................................ E. anamallayanum Beddome (1874: 33) 14. Succulent herbs with a pincushion habit ..........................................................................................................................................15 - Slightly to much-branched ascending herbs.................................................................................................................. E. laxiflorum 15 Flowers solitary, long-pedicellate.......................................................................................... E. travancoricum Beddome (1874: 24) - Flowers in multiflorous cymes, short-pedicellate ....................................................................................................... E. courtallense