| 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 |
| Sergio C. de Sant'Ana |
Spermatophytes |
| Henry P. Sartwell |
Spermatophytes; Cyperaceae; Bryophytes; Algae; Characeae |
| Albert Schneider |
Algae; Lichens; Mycology |
| Irma Schnooberger |
Bryophytes |
| Wilfred B. Schofield |
Bryophytes |
| Arthur C. V. Schott |
Algae; Bryophytes; Spermatophytes |
| Carl A. Schwarze |
Mycology |
| George W. Scotter |
Spermatophytes; Bryophytes; Lichens |
| Fred J. Seaver |
Mycology; Discomycetes; Lichens |
| Augustine D. Selby |
Algae; Mycology |
| John A. Shafer |
Algae; Pteridophytes; Spermatophytes; Mycology; Bryophytes |
| Aaron J. Sharp |
Algae; Bryophytes; Mycology; Spermatophytes |
| Carleton A. Shurtleff |
Spermatophytes |
| Marcos Silveira |
Spermatophytes; Ecology of arborescent bamboos; systematic botany, plant ecology; flora of Southwestern Amazonia |
| John Kunkel Small |
Algae; Bryophytes; Pteridophytes; Spermatophytes; Lichens |
| Lyman B. Smith |
Spermatophytes; Pteridophytes; Lichens |
| Herbert H. Smith |
Spermatophytes; Bryophytes; Lichens |
| Albert C. Smith |
Algae; Spermatophytes; Pteridophytes; Bryophytes; Lichens |
| Richard Spruce |
Bryophytes; Pteridophytes; Spermatophytes; Lichens |
| Howard Stansbury |
Spermatophytes |
| William C. Steere |
Bryophytes; Lichens |
| Julian A. Steyermark |
Pteridophytes; Spermatophytes; Angiosperms; Bombacaceae; Bryophytes; Algae; Characeae; Lichens |
| Arlow B. Stout |
Bryophytes; Spermatophytes; Hemerocallis |
| William C. Sturgis |
Algae; Cryptogams; Mycology; Bryophytes; Spermatophytes |
| William S. Sullivant |
Bryophytes; Algae; Mosses; Spermatophytes |