| Xenosia macrorhiza (Lindl.) Luer | = | Stelis purpurea (Ruiz & Pav.) Willd. |
| Xenosia spiralis (Ruiz & Pav.) Luer | = | Stelis purpurea (Ruiz & Pav.) Willd. |
| Xiphosium acuminatum Griff. | = | Eria carinata Gibson |
| Xylobium powellii Schltr. | = | Xylobium sulfurinum (Lem.) Schltr. |
| Xylobium tuerckheimii Kraenzl. | = | Xylobium sulfurinum (Lem.) Schltr. |