| Melanthiaceae | ** |
Zygadenus brevibracteatus
| H.M. Hall | | |
| Melanthiaceae | ** |
Zygadenus densus
| Fernald | | |
| Melanthiaceae | ** |
Zygadenus elegans
| Pursh | | |
| Melanthiaceae | ** |
Zygadenus exaltatus
| Eastw. | | |
| Melanthiaceae | ** |
Zygadenus fremontii
| Torr. | Botany (Fortieth Parallel) 343 | 1871 |
| Melanthiaceae | ** |
Zygadenus glaberrimus
| Michx. | | |
| Melanthiaceae | ** |
Zygadenus glaucus
| Nutt. | | |
| Melanthiaceae | ** |
Zygadenus leimanthoides
| A. Gray | | |
| Melanthiaceae | ** |
Zygadenus micranthus
| Eastw. | | |
| Melanthiaceae | ** |
Zygadenus nuttallii
| S. Watson | | |
| Melanthiaceae | ** |
Zygadenus paniculatus
| S. Watson | | |
| Melanthiaceae | * |
Zygadenus porrifolius
| Greene | | |
| Melanthiaceae | ** |
Zygadenus venenosus
| S. Watson | | |
| Melanthiaceae | ** |
Zygadenus virescens
| McBride | | |
| Melanthiaceae | ** |
Zygadenus volcanicus
| Benth. | Pl. Hartw. 96 | 1842 |