Thrixspermum, Loureiro, 1790

Kumar, Vikas, Verma, Durgesh & Rao, Abbareddy Nageswara, 2017, Thrixspermum indicum (Orchidaceae), a new species from Northeast India, Phytotaxa 292 (1), pp. 79-84 : 83

Key to the species of Genus Thrixspermum from India :

1a. Flowers arranged in two alternate rows on the rachis of inflorescence.............................................................................................2

1b. Flowers arranged all around the rachis facing all directions..............................................................................................................6

2a. Sepals and petals long narrowly acuminate........................................................................................................................................3

2b. Sepals and petals relatively shorter and broader................................................................................................................................4

3a. Mid-lobe of lip narrowly acuminate................................................................................................................... T. acuminatissimum

3b. Mid-lobe of lip terete and obtuse...................................................................................................................................... T. centipeda

4a. Leaves short, ovate, amplexicaule; flowers pale violet.............................................................................................. T. amplexicaule

4b. Leaves oblong; flowers yellow or white............................................................................................................................................5

5a. Inflorescence 2–3 cm long; flowers white with yellow lip ......................................................................................... T. pauciflorum

5b. Inflorescence 10–12 cm long; flowers golden yellow............................................................................................... T. complanatum

6a. Lip without any hair on mid-lobe or lateral lobes; hair restricted to saccate spur only.....................................................................7

6b. Lip with dense or sparsely arranged hair on disc, mid-lobe or lateral lobes......................................................................................8

7a. Leaves broader, about 2.5 cm, entire and acute at apex ................................................................................................ T. crassilabris

7b. Leaves narrower, up to 1.5 cm, obtuse and bi-lobed at apex.............................................................................................. T. indicum

8a. Hair present in clusters on the lip.......................................................................................................................................................9

8b. Hair not in clusters but uniformly scattered on lip inner surface and margins.................................................................................10

9a. Hair present in three clusters on mid-lobe of lip ............................................................................................................ T. merguense

9b. Hair present in one cluster on centre of disc of lip........................................................................................................ T. saruwatarii

10a. Flowers yellow.................................................................................................................................................................................11

10b. Flowers white...................................................................................................................................................................................13

11a. Lip white; hair on front margins of lip lobes shorter and not gland-tipped.............................................................. T. muscaeflorum

11b. Lip yellow; hair on front margins longer and gland-tipped..............................................................................................................12

12a. Glandular hair present on outer surface of mid-lobe and lateral lobes of lip ................................................................. T. pygmaeum

12b. Glandular hair absent on outer surface of lip lobes.............................................................................................................. T. hystrix

13a. Sepals and petals acute at apex; glandular hair on apical margins of lateral lobes and mid-lobe of lip strikingly longer................... ...................................................................................................................................................................................... T. trichoglottis

13b. Sepals and petals obtuse at apex; glandular hair on front margins of lip comparatively much shorter...........................................14

14a. Leaves linear, acute; flowers opening successively ................................................................................................... T. formosanum

14b. Leaves oblong, bi-lobed at apex; flowers opening simultaneously............................................................................... T. pulchellum