| Name | Collema nigrescens f. caesium (Clements) Acharius |
| Authorship | (Clements) Acharius |
| Rank | Forma |
| Placed in | Collema nigrescens (Hudson) de Candolle |
| GUID | urn:lsid:indexfungorum.org:names:122577 |
| Holdings | 30 Specimens held in the Harvard University Herbaria identified as Collema nigrescens f. caesium (Clements) Acharius |
| Identification made in | [no date] (30) |