| 1 | Plants very finely pubescent; triads 2, peduncle extremely delicate; petals 4 |
| 1' | Plants glabrous throughout; triads mostly numerous, sessile or nearly so, or peduncles not delicate; petals 3-6 |
| 2 | Plants very slender; leaves very narrowly lanceolate, mostly < 5 x 1 cm, venation obscure except for midrib; triads 2-4 pair per inflorescence |
| 2' | Plants not unusually slender; leaves ovate or at least not narrowly lanceolate, mostly > 6 x 2 cm, venation pinnate, evident; triads mostly > 5 pairs per inflorescence |
| 3 | Inflorescence peduncles conspicuously flattened or winged |
| 3' | Inflorescence peduncles terete or only slightly angled |
| 4 | Inflorescence axis strongly brown-furfuraceous; leaf apex acute, base truncate or nearly so; dioecious |
| 4' | Inflorescence axis glabrous or no more than very thinly furfuraceous; leaf apex acute to rounded, base obtuse to acute; dioecious or flowers bisexual |
| 5 | Leaf apex acute |
| 5' | Leaf apex obtuse to rounded |
| 6 | Flowers bisexual; epicortical roots from base only; stems compressed or even keeled when young, with furfuraceous lines |
| 6' | Plants dioecious; epicortical roots from base and at least sometimes from stem; young stems no more than slightly compressed, not keeled, lacking furfuraceous lines |
| 7 | Leaves narrowly ovate, base acute; inflorescence with 3-6 pairs of triads |
| 7' | Leaves broadly ovate, base usually obtuse; inflorescence with to 12 or more pairs of triads |
| 8 | Inflorescence umbellate or essentially so, at least when young, sometimes nearly sessile in leaf axil; flowers 6-merous |
| 8' | Inflorescence a (mostly pedunculate) spike or raceme; flowers (3-) 4-merous |
| 9 | Members of a triad pair often separated along elongating inflorescence axis; triad bract broad, investing base of fruit; leaves thin, often mucronate or emarginate |
| 9' | Inflorescence axis not elongating, triads strictly paired; triad bract not investing base of fruit; leaves coriaceous, not mucronate or emarginate |
| 10 | Inflorescence axillary only; bracts and bracteoles distinct, persistent on lower part of spikes; anthers alternatingly 2- and 4-loculate; dioecious, only male ones known |
| 10' | Inflorescence axillary and often in terminal compound clusters; bracts and bracteoles forming a deciduous cupule, leaving lower part of peduncle naked; anthers 2-loculate only; flowers bisexual |
