Acianthera species

Gomez, Rodolfo Solano, 2015, A taxonomic synopsis of the Mexican species of Acianthera (Orchidaceae: Pleurothallidinae) including a new species, Phytotaxa 218 (1), pp. 39-60 : 57

Key for Mexican Acianthera species

1. Plants long repent; inflorescence apparently a 1- or 2-flowered raceme .......................................................................................... 2

- Plants cespitous or short repent; inflorescence a many or multi-flowered raceme............................................................................3

2. Plants pendent; leaves sub-orbicular; sepals pubescent on the abaxial surface ................................................. Acianthera testifolia

- Plants erect, leaves lanceolate; sepals glabrous on abaxial surface............................................................... Acianthera angustifolia

3. Stems with more than three apparent internodes, covered with laterally compressed sheaths, inflated toward the apex; inflorescence from the stem base (sometimes from the apex)....................................................................................................................... 4

- Stems with two apparent internodes, covered with tubular, adpressed sheaths; inflorescence only from the apex stem ................. 6

4. Sepals glabrous or cellular-papillose on both surfaces; lip oblong-obovate ...................................................... Acianthera johnsonii

- Sepals pubescent on one or both surfaces; lip unguiculate or hastate................................................................................................5

5. Lip hastate, with lateral lobes rounded and erect ................................................................................................ Acianthera sotoana

- Lip unguiculate, with lateral lobes filiform and uncinate................................................................................... Acianthera herrerae

6. Leaves narrowly lanceolate or elliptic (at least 5 times longer than wide)........................................................................................7

- Leaves ovate, lanceolate or elliptic (less than 4 times longer than wide)..........................................................................................9

7. Raceme shorter than half of the leaf and successively flowered.......................................................................... Acianthera obscura

- Raceme as long as half of the leaf or longer, simultaneously multi-flowered...................................................................................8

8. Sepals abaxially short pubescent, the dorsal one oblanceolate; petals obovate ............................................... Acianthera breedlovei

- Sepals abaxially glabrous, the dorsal one lanceolate; petals oblanceolate.................................................... Acianthera hondurensis

9. Leaves with margins decurrent along the stem; raceme emerges above the leaf base.................................. Acianthera circumplexa

- Leaves without margins decurrent along the stem; raceme emerging from the leaf base................................................................10

10. Stems 3-angled in cross-section; leaves fleshy; floral bracts conspicuously overlapped................................................................11

- Stems cylindrical in cross-section; leaves coriaceous; floral bracts not or only slightly overlapped..............................................14

11. Sepals papillose or apparently glabrous on the outer surface........................................................................ Acianthera greenwoodii

- Sepals densely pubescent on the outer surface.................................................................................................................................12

12. Flowers tubular, 12 − 13 mm long; margins of dorsal sepal and synsepal jointed along their length ............ Acianthera pollardiana

- Flowers bilabiate, 5 − 6 mm long; margins of the dorsal sepal and synsepal only united at the bases..............................................13

13. Leaves extremely fleshy, adaxially reticulate-rouge when dry; flowers yellowish or brownish; dorsal sepal apically incurved........ ........................................................................................................................................................................ Acianthera chrysantha

- Leaves fleshy, adaxially not reticulate when dry; flowers orange; dorsal sepal apically recurved........... Acianthera hartwegiifolia

14. Flowers shortly tubular or subglobose; lateral sepals united to the dorsal one up to halfway; petals linear, marginally entire ..... 15

- Flowers bilabiate; lateral sepals united to the dorsal one at the base; petals obovate or hastate, marginally dentate..................... 17

15. Lateral sepals fused up to halfway; lip oblanceolate when extended; plants from the Revillagigedo islands (Pacific ocean)............ ..................................................................................................................................................................... Acianthera unguicallosa

- Lateral sepals totally fused; lip hastate when extended; plants from continental Mexico...............................................................16

16. Flowers subglobose; plants from Veracruz, Chiapas and Northern Oaxaca ........................................................ Acianthera violacea

- Flowers shortly tubular; plants from Southern Oaxaca .......................................................................................... Acianthera eximia

17. Sepals adaxially purple stripped, the dorsal one strongly deflexed at the mid; plants from low elevations with warm-wet climate.. ........................................................................................................................................................................... Acianthera tikalensis

- Sepals adaxially purple doted, the dorsal one no deflexed or slightly incurved at the apex; plants from mid elevations with temperate-wet climate..................................................................................................................................................................................18

18. Sepals abaxially short pubescent, the dorsal one narrowly lanceolate; petals oblanceolate ....................... Acianthera angustisepala

- Sepals abaxially glabrous, the dorsal one lanceolate; petals hastate................................................................................................19

19. Leaves oblong, less than 2 cm in wide; plants from wet environments........................................................... Acianthera pubescens

- Leaves ovate to elliptic, more than 2 cm in wide; plants from xeric environments.................................... Acianthera majakoluckae