Synoptic key to the long-tubed Malagasy Ixora species (corolla tube < 15 cm)

1a Leaves verticillate, in whorls of 3 or 4; petioles up to 0.5 cm long; leaf blades with cordate to rounded base; stipules consisting of a large triangular sheath, 20-33 mm long, needle-like awn absent; inflorescences compact, non-articulate; fruits markedly lageniform ..................................... Ixora peculiaris
1b Leaves decussate, in pairs; petioles (0.5-)1-3 cm long; leaf blades with cuneate, acute, or rarely rounded base; stipules consisting of a basal sheath topped by a needle-like awn, 3-13 mm long, needle-like awn 1-6 mm long; inflorescences lax or compact, at least partly articulate; fruits never lageniform ...................................................................................................................................................................... 2

2a Inflorescences moderately to long pedunculate, peduncle 5-42 cm long; modified inflorescence-supporting leaves present; bracts and bracteoles well-developed; bracteoles broadly triangular, 2.5-6 mm long; pedicels 0-7 mm long, the pedicel of the central flower short (0-1 mm long); calyx with well-developed triangular lobes; flowers articulate; leaves not drying yellowish .......................... 3
2b Inflorescences sessile to very shortly pedunculate, peduncle B1.5 cm long; modified inflorescence-supporting leaves absent; bracts and bracteoles absent or reduced; bracteoles, if present, filiform, ca 0.5 mm long; pedicels (2-)5-15 mm long; calyx (sub-)truncate; flowers not articulate; leaves usually drying yellowish ................................................................................................................... Ixora crassipes

3a Inflorescences compact, with numerous flowers; corolla tubes 18-23 cm long ..........................................
........................................................................................................................................................... Ixora densithyrsa
3b Inflorescences lax, with 12-100 flowers; corolla tubes (10-)15-22 cm long ..................................................
.......................................................................................................................................................... Ixora siphonantha

Adapted from: De Block (2007) Three new Madagascan Ixora species (Rubiaceae) with flowers up to 23 cm long. Nordic Journal of Botany 25: 75-84, 2007