| Tetrachyron websteri (Wussow & Urbatsch) B.L. Turner, 1988 |
| Tetradymia DC., 1838 |
| Tetradymia comosa A. Gray, 1877 |
| Tetragonotheca L., 1753 |
| Tetragonotheca texana A. Gray & Engl., 1846 |
| Tetraneuris Greene, 1898 |
| Tetraneuris linearifolia (Hook.) Greene, 1898 |
| Tetraneuris linearifolia var. linearifolia (Hook.) Greene, 1898 |
| Tetraneuris scaposa (DC.) Greene, 1898 |
| Tetraneuris scaposa var. argyrocaulon (K.F. Parker) K.F. Parker, 1980 |
| Tetraneuris scaposa var. scaposa (DC.) Greene, 1898 |
| Tetraneuris turneri (K.F. Parker) K.F. Parker, 1980 |
| Thelechitonia Cuatrec., 1954 |
| Thelesperma Less., 1831 |
| Thelesperma ambiguum A. Gray, 1883 |
| Thelesperma burridgeanum (Regel) S.F. Blake, 1928 |
| Thelesperma filifolium A. Gray, 1849 |
| Thelesperma filifolium var. filifolium A. Gray, 1849 |
| Thelesperma filifolium var. intermedium (Rydb.) Shinners, 1966 |
| Thelesperma graminiformis (Sherff) Melchert, 1990 |