| Alice M. Ottley |
Spermatophytes |
| Matthew Charles Pace |
Orchidaceae; Spermatophytes |
| Stuart M. Pady |
Mycology |
| Edward Palmer |
Algae; Bryophytes; Spermatophytes |
| Charles C. Parry |
Algae; Bryophytes; Spermatophytes |
| Paul Morrison Patterson |
Bryophytes; Mycology; Musci |
| Paola Pedraza-Peñalosa |
Colombian plants; Ericaceae; Andes; Spermatophytes |
| Francis W. Pennell |
Spermatophytes; Scrophulariaceae |
| George W. Perry |
Algae |
| Nicolas Pike |
Algae; Bryophytes |
| Ann P. Pinzl |
Spermatophytes |
| Ghillean T. Prance |
Spermatophytes; Chrysobalanaceae; Bryophytes; Lichens |
| Cyrus G. Pringle |
Algae; Bryophytes; Mycology; Spermatophytes |
| Eugene Abraham Rau |
Bryophytes; Mycology; Algae; Musci; Pteridophytes; Phanerogams; Cryptogams |
| Paul L. Redfearn, Jr. |
Bryophytes; Spermatophytes |
| Clyde F. Reed |
Algae; Bryophytes; Pteridophytes; Spermatophytes; Lichens |
| William Dean Reese |
Bryophytes; Musci; Lichens |
| Padre Raulino Reitz |
Spermatophytes |
| Herbert M. Richards |
Algae |
| Ludwig Riedel |
Spermatophytes |
| Clark T. Rogerson |
Mycology; Lichens |
| Joseph N. Rose |
Algae; Bryophytes; Cactaceae; Ferns; Fungi; Spermatophytes |
| Henry H. Rusby |
Algae; Spermatophytes; Bryophytes; Lichens |
| Per Axel Rydberg |
Algae; Bryophytes; Mycology; Phanerogams; Pteridophytes; Spermatophytes |
| Gary J. Samuels |
Mycology; Bryophytes; Lichens |