1. Climbing plants; calyx minute, annular or 10-15 toothed………21. Thunbergia1. Prostrate or erect plants; calyx usually deeply divided:2. Corlla segments imbricate in buds; fertile stamens 2 or 4:3. Fertile stamens 2:4. Seeds without retinacula………………………………12. Nelsonia4.
Seeds with retinacula:5. Ovary cells 6-10 ovules…………………………………16. Phologacanthus 5. Ovary cells 2-ovules:6. Corolla lobes sub equal, not distinctly 2-lipped………………6. Eranthemum 6.
Corolla distinctly 2-lipped:7. Flowers in lax cymes or panicles; anther cell without a basal spur:8. Flowers purplish-lilac; bracts mucroante, clustered………….5. Dicliptera8. Flowers pink-purple; bracts in opposite pairs, valvate, not mucronate……………………………………………………14. Peristrophe 7. Flowers in dense spikes; anther cells with a basal spur at the base:9.
Bracts dimorphic………………………………………..……19. Rungia9. Bracts not dimorphic:10.
Corolla white, more than 1.5 cm long………………………1. Adhatoda 10. Corolla pinkish-purple, less than 1 cm long……………….
..10. Justicia 3. Fertile stamens 4:11. Calyx segments 5; anther cells basally spurred………………3. Asystasia11.
Calyx segments 4 or 5; anther cells not spurred: 12. Spikes not aggregated; 2 stamens exserted, 2 rudimentary……4. Barleria12. Spikes aggregated in globose heads; stamens all fertile, included…………………………………………….
.11. Lepidagathis2. Corolla segments contracted in buds; fertile stamens 4:13.
Ovary cells 3-7 ovuled; cells of the capsules 3 or more seeded:14. Corolla distinctly 2-lipped……………………………………9. Hygrophila 14. Corolla not distinctly 2-lipped, subequally 5-libed:15. Flowers in capitates spikes……………………………………8. Hemigraphis 15. Flowers in clusters, combined into a panicle…………………2.
Aechmanthera13. Ovary cells 1-2 ovuled; cells of the capsules 1-2 seeded:16. Anther cells basally spured……………………………………15. Petalidium16.
Anther cells not spured:17. Leaves sessile with ampexicaule base; flowers in dense spikes…13. Perilepta17. Leaves petioled not ampexicaule; flowers in capitates or elongated spikes:18.
Flowers in capitate spikes:19. Bracts caducous, not leaf like…………………………..7. Goldfussia 19.
Bracts persistent leaf like……………………………20. Strobilanthes 18. Flowers in elongated racemes:20. Bracts persistent; corolla purplish……………………17. Pseudoaechmanthera20. Bracts caducous; corolla blue-purple………………..
18. Pteracanthus
