| 1 | Leaves opposite or in whorls of 1-7 |
| 1' | Leaves alternate |
| 2 | Leaf apex acute or somewhat acuminate |
| 2' | Leaf apex obtuse, rounded or emarginate |
| 3 | Stem glabrous; leaves glabrous; spikes 10-16 cm long; fruit with apical stigma |
| 3' | Stem villous; leaves pubescent; spikes 2.5-15 cm long; fruit with subapical stigma |
| 4 | Leaves opposite |
| 4' | Leaves in whorls of 1-7 |
| 5 | Stem minutely hirtellous; leaf margin not ciliate; peduncle without bracts |
| 5' | Stem minutely pubescent; leaf margin ciliate; peduncle 2-bracteate |
| 6 | Stem glabrous |
| 6' | Stem variously pubescent |
| 7 | Fruit slightly stipitate at maturity; stigma apical |
| 7' | Fruit (sub)basely attached, not stipitate; stigma apical on short, thick style, or fruit with small beak and subapical stigma, or fruit apex oblique with subapical stigma |
| 8 | Rachis of spike pubescent; fruits sunken in rachis |
| 8' | Rachis of spike glabrous; fruits (sub)basely attached, not sunken |
| 9 | Spikes to 15 cm long, terminal or axillary, often in groups of 2-5; leaf blade 0.2-0.6 mm wide, apex obtuse; fruit apex oblique with subapical stigma |
| 9' | Spikes 2-7 cm long, terminal and solitary; leaf blade 0.6-2.3 cm wide; apex rounded to emarginate; fruit with short, thick style and apical stigma |
| 10 | Spikes in panicles |
| 10' | Spikes simple, solitary, 2-few together or bifurcate |
| 11 | Leaves distinctly peltate |
| 11' | Leaves basely attached or slightly peltate |
| 12 | Leaf apex rounded, blade with erect trichomes at upper surface; petiole attached centrally; fruit flat at apex |
| 12' | Leaf apex somewhat acute to acuminate, blade glabrous or minutely pubescent; petiole attached between base and leaf centre, 0.2-3 cm from base; fruit with slender beak |
| 13 | Stem and leaf blade minutely pubescent; petiole 3-11(-16) cm long |
| 13' | Stem and leaf blade glabrous; petiole 1.5-6 cm long |
| 14 | Leaf apex rounded or emarginate |
| 14' | Leaf apex acuminate, acute to obtuse |
| 15 | Stem and leaf blade glabrous; blade 2-14 cm long; spikes 2-18 cm long |
| 15' | Stem and leaf blade crisp-pubescent or minutely hirtellous; blade less than 2 cm long; spikes to 2 cm long |
| 16 | Petiole not grooved or winged; peduncle as long as or longer than spikes; spikes 2-5 cm long |
| 16' | Petiole grooved or winged; peduncle as long as or shorter than spikes; spikes to 18 cm long |
| 17 | Leaf blade in vivo fleshy; floral bracts 5-7 mm in diam.; fruit subglobose |
| 17' | Leaf blade in vivo coriaceous; floral bracts 2-4 mm in diam.; fruit ellipsoid |
| 18 | Leaf apex emarginate; stem glabrous, sparsely villous or minutely hirtellous |
| 18' | Leaf apex rounded; stem crisp-pubescent |
| 19 | Stem minutely hirtellous; leaf blade 0.5-0.8 x 0.5-1 cm; fruit crowned with persistent, conic style, stigma mammiform; above 2000 m elev. |
| 19' | Stem glabrous or sparsely villous; leaf blade 0.15-0.6 cm in diam.; fruit with apical stigma, not mammiform; from sealevel up to 600 m elev. |
| 20 | Leaf blade broadly elliptic to deltoid; peduncle nodose or with 1-2 (falling off early) bracts, often longer than flowering rachis; fruit ellipsoid |
| 20' | Leaf blade almost circular, broadly elliptic or elliptic; peduncle not nodose, without bracts, usually shorter than flowering rachis; fruit globose to ovoid |
| 21 | Terrestrial herbs |
| 21' | Epiphytic or epilithic, occasionally terrestrial herbs |
| 22 | Leaf blade broadly elliptic to deltoid, 1-3.7 cm long; spikes terminal, to 6 cm long |
| 22' | Leaf blade ovate, to 12 cm long; spikes axillary, to 17 cm long |
| 23 | Leaf base truncate, cord(ul)ate or rounded; spikes 1-5 cm long |
| 23' | Leaf base cuneate, acute to obtuse; spikes 1.5-30 cm long |
| 24 | Leaf blade 0.8-2.5 x 0.8-2.5 cm; spike axillary, 1-2.5 cm long, shorter than peduncle |
| 24' | Leaf blade 2-3 x 2.7-7 cm; spike terminal, 1.5-5 cm long, about as long as peduncle |
| 25 | Older leaf blades 4-20 cm long; spikes 4-30 cm long |
| 25' | Older leaf blades less than 4 cm long; spikes 1.5-7 cm long |
| 26 | Whole plant strongly glandular dotted (black when dried); petiole usually with 2 rows of hairs; peduncle glabrous |
| 26' | Plants at most somewhat glandular, not black-dotted when dried; no lines of hairs on petiole; peduncle glabrous or minutely puberulous |
| 27 | Internodes of stem longitudinally ridged or winged; petiole deeply grooved, glabrous; fruits laterally attached, globose-ovoid |
| 27' | Internodes not winged nor ridged; petiole narrowly winged or not, glabrous or sparsely, minutely puberulent; fruits basely attached, cylindrical or ellipsoid |
| 28 | Leaf blade narrowly elliptic to ovate, upper surface usually covered with waxy exudate forming star- or scale-like structures; spikes to 30 cm long; growing on ant’s nests |
| 28' | Leaf blade narrowly elliptic to obovate, upper surface not covered with waxy exudate; spikes to 18 cm long; not growing on ant's nest |
| 29 | Leaf blade 1-3 cm wide, apex acuminate; fruits with short beak |
| 29' | Leaf blades 2.5-6 cm wide, apex at most acute; fruits tapering into a slender beak, which is slightly hooked at very tip |
| 30 | Leaf blade 0.8-2.3 cm wide, often, or at least at veins, red below; spikes 5-7 cm long |
| 30' | Leaf blade less than 1 cm wide, green; spikes to 5.5 cm long |
| 31 | Leaf blade villous, apex obtuse; veins obvious; fruit sessile |
| 31' | Leaf blade glabrous or shortly puberulous, apex obtuse and minutely emarginate with some hairs in the indentation; veins obsolete; fruit stipitate at maturity |
