| | 1. Twig-leaves not overlapping, strongly clasping, abruptly pointed; sepals ± round |
| T. aphylla |
| | 1' Twig-leaves overlapping, not clasping, acute to long-acuminate; sepals elliptic to ovate |
| |
| | 2. Sepals, petals, and stamens generally 4 |
| T. parviflora |
| | 2' Sepals, petals, and stamens generally 5 |
| |
| | 3. Nectar disk lobes longer than wide, confluent with filaments |
| T. gallica |
| | 3' Nectar disk lobes wider than long, alternate filaments |
| |
| | 4. Leaves oblong to narrowly lanceolate, acute; sepals entire |
| T. chinensis |
| | 4' Leaves ovate, acute to acuminate; sepals minutely toothed |
| T. ramosissima
|