| 1 | Calyx detaching at anthesis circumscissile from the base and falling off in one piece as a calyptra. Stamens ∞, except 5 or (8-) 10 in 3 spp. |
| 1' | Calyx bursting irregularly at anthesis: toothed or lobed, andfor splitting on one side (spathaceous), and then detaching circumscissile. Stamens (4 or) 5 (or 6). |
| 2 | Stamens ∞ (c. 20-100). |
| 2' | Stamens 5-10. |
| 3 | Ovary hairy. Leaves pubescent beneath, especially on the midrib, nerves, and veins. |
| 3' | Ovary glabrous (rarely scurfy in G. rugulosa). Leaves glabrous, rarely slightly hairy beneath when young, glabrescent. |
| 4 | Inflorescences accompanied by mature leaves. Petals obovate-oblong or -lanceolate |
| 4' | Inflorescences appearing before the leaves or accompanied by some young ones. Petals elliptic-lanceolate or lanceolate |
| 5 | Mature flower-bud or calyptra-shaped calyx more than 3 mm wide. Petals contorted or imbricate. Stamens more than 35. |
| 5' | Mature flower-bud or calyptra-shaped calyx 1½-2 mm wide. Petals almost valvate except at the apical part. Stamens c. 20(-28) |
| 6 | Apex of the calyptra-shaped calyx obtuse, acute, or acuminate. |
| 6' | Apex of the calyptra-shaped calyx rostrate |
| 7 | Pedicels not articulated. Ovary with a shorter stipe (between ovary and stamens) ½-2 mm long. |
| 7' | Pedicels articulated. Ovary with a stipe (between ovary and stamens) (2-)3-5 mm long |
| 8 | Calyx usually with a tuft of hairs at the apex, sometimes puberulous outside when young and glabrescent except the apical part. Petals oblanceolate, 11-16 mm long |
| 8' | Calyx densely puberulous outside. Petals elliptic-oblong or ovate-oblong, 7½-9 mm long |
| 9 | Stamens (8-) 10. Leaves distinctly petioled (¾-2½ cm); nerves 9-18 pairs, distinct beneath. |
| 9' | Stamens 5. Leaves with obscure or very short petiole (c. ½ cm); nerves 17-27 pairs, prominent beneath |
| 10 | Inflorescences puberulous, glabrescent. Pedicels 1½-2½ mm, articulated. Petals contorted or imbricate |
| 10' | Inflorescenses glabrous. Pedicels 8-16 mm, not articulated. Petals valvate |
| 11 | Ovary hairy. |
| 11' | Ovary glabrous. |
| 12 | Petals with the basal ¾-3 mm longitudinally adnate to the cylindric torus. Pedicels not articulated. |
| 12' | Petals with the base attached to the base of the pulvinate torus, not adnate. Pedicels articulated |
| 13 | Petals 5-7½ mm long. Leaves usually pseudo-verticillate. |
| 13' | Petals 8-13 mm long. Leaves scattered. |
| 14 | Petals densely puberulous on both surfaces. Torus c. 1½ mm long. Stipe of the ovary 1-1½ mm long; style terminal |
| 14' | Petals puberulous outside and densely papillose usually at the lower half inside. Torus 1-1½45 mm long. Stipe of the ovary obscure; style lateral |
| 15 | Petals narrowly elliptic, 8-9 by 1½45-2 mm |
| 15' | Petals narrowly oblanceolate, 10-13 by 2½ mm |
| 16 | Torus 3½-7 mm long. Pedicels not articulated. Petals puberulous outside (except in G. elegans). |
| 16' | Torus ½4-3 mm long. Pedicels articulated. Petals glabrous outside. |
| 17 | Inflorescences branched from the apical part. Flowers crowded at the end of branchlets |
| 17' | Inflorescences branched almost from the base. Flowers laxly arranged on the branchlets. |
| 18 | Petals with the basal 5-6 mm completely adnate to the torus |
| 18' | Petals with the central part of the basal 3½-5½ mm adnate to the torus. |
| 19 | Torus 3½ mm long. Leaves with slightly elevated nerves, sometimes hardly distinguishable from the veins on both surfaces |
| 19' | Torus 5-6 mm long. Leaves with slightly elevated nerves distinguishable from the veins on both surfaces |
| 20 | Calyx puberulous outside. Leaf apex acuminate. Large shrub or small tree up to 10 m high |
| 20' | Calyx glabrous except sparsely hairy at the apex. Leaf apex obtuse, rounded, or slightly emargi-nate, rarely cuspidate. Tall trees. |
| 21 | Torus ½4-l½45 mm long. Petals 6½-7½ mm long |
| 21' | Torus 2-3 mm long. Petals 7½-l3 mm long |
