| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| RAHE6 | Radicula heterophylla (Blume) Small | Rorippa indica var. indica | Brassicaceae
|
| RAHI3 | Radicula hispida (Desv.) Britt. | Rorippa palustris ssp. hispida | Brassicaceae
|
| RAOB3 | Radicula obtusa (Nutt.) Greene | Rorippa teres | Brassicaceae
|
| RAPA7 | Radicula palustris (L.) Moench | Rorippa palustris ssp. palustris | Brassicaceae
|
| RAPO3 | Radicula portoricensis (Spreng.) Britt. | Rorippa portoricensis | Brassicaceae
|
| RASE3 | Radicula sessiliflora (Nutt.) Greene | Rorippa sessiliflora | Brassicaceae
|
| RASIT | Radicula sinuata (Nutt.) Greene var. truncata Jepson | Rorippa curvipes var. truncata | Brassicaceae
|
| RASI | Radicula sinuata (Nutt.) Greene | Rorippa sinuata | Brassicaceae
|
| RASP2 | Radicula sphaerocarpa (Gray) Greene | Rorippa sphaerocarpa | Brassicaceae
|
| RASY | Radicula sylvestris (L.) Druce | Rorippa sylvestris | Brassicaceae
|
| RAWA2 | Radicula walteri (Ell.) Greene | Rorippa teres | Brassicaceae
|
| RALI | Radiola linoides Roth | allseed | Linaceae
|
| RADIO | Radiola Hill | radiola | Linaceae
|
| RAAU5 | Radula auriculata Steph. | | Radulaceae
|
| RAAU6 | Radula australis Austin | | Radulaceae
|
| RABO5 | Radula bolanderi Gottsche | | Radulaceae
|
| RABR13 | Radula brunnea Steph. | | Radulaceae
|
| RACOC | Radula complanata (L.) Dumort. ssp. complanata | | Radulaceae
|
| RACOL | Radula complanata (L.) Dumort. ssp. lindenbergiana R. M. Schust. | | Radulaceae
|
| RACO19 | Radula complanata (L.) Dumort. | | Radulaceae
|
| RAFL5 | Radula flaccida Lindenb. & Gottsche | | Radulaceae
|
| RAFL6 | Radula floridana Castle | | Radulaceae
|
| RAMO6 | Radula mollis Lindenb. & Gottsche | | Radulaceae
|
| RAOB5 | Radula obconica Sull. | | Radulaceae
|
| RAOBP | Radula obtusiloba Steph. ssp. polyclada (A. Evans) S. Hatt. | | Radulaceae
|
| RAOB6 | Radula obtusiloba Steph. | | Radulaceae
|
| RAPR4 | Radula prolifera S. W. Arnell | | Radulaceae
|
| RASU17 | Radula sullivantii Austin | | Radulaceae
|
| RATE12 | Radula tenax Lindb. | | Radulaceae
|
| RAVO2 | Radula voluta Taylor | | Radulaceae
|
| RADUL | Radula Dumort. nom. cons. | | Radulaceae
|
| RACA | Rafinesquia californica Nutt. | California plumseed | Asteraceae
|
| RANE | Rafinesquia neomexicana Gray | New Mexico plumseed | Asteraceae
|
| RAFIN | Rafinesquia Nutt. | California chicory | Asteraceae
|
| RAAR | Raillardella argentea (Gray) Gray | silky raillardella | Asteraceae
|
| RAMI5 | Raillardella minima Rydb. | Raillardella argentea | Asteraceae
|
| RAMU | Raillardella muirii Gray | Raillardiopsis muirii | Asteraceae
|
| RAPR | Raillardella pringlei Greene | showy raillardella | Asteraceae
|
| RASC | Raillardella scabrida Eastw. | Raillardiopsis scabrida | Asteraceae
|
| RASC2 | Raillardella scaposa (Gray) Gray | stem raillardella | Asteraceae
|
| RAILL | Raillardella (Gray) Benth. | raillardella | Asteraceae
|
| RAAR6 | Raillardia argentea Gray | Raillardella argentea | Asteraceae
|
| RAMU3 | Raillardiopsis muirii (Gray) Rydb. | Muir's raillardiopsis | Asteraceae
|
| RASC4 | Raillardiopsis scabrida (Eastw.) Rydb. | leafy raillardiopsis | Asteraceae
|
| RAILL3 | Raillardiopsis Rydb. | raillardiopsis | Asteraceae
|
| RAAR4 | Railliardia arborea Gray | Dubautia arborea | Asteraceae
|
| RACIJ | Railliardia ciliolata DC. var. juniperoides Gray | Dubautia ciliolata ssp. ciliolata | Asteraceae
|
| RACIL | Railliardia ciliolata DC. var. leptocephala O. Deg. & Sherff | Dubautia linearis ssp. hillebrandii | Asteraceae
|
| RACIT | Railliardia ciliolata DC. var. trinervia (Hbd.) Keck p.p. | Dubautia menziesii | Asteraceae
|
| RACI3 | Railliardia ciliolata DC. | Dubautia ciliolata ssp. ciliolata | Asteraceae
|
| RADED | Railliardia demissifolia Sherff var. dolichophylla St. John | Dubautia thyrsiflora | Asteraceae
|
| RADE3 | Railliardia demissifolia Sherff | Dubautia demissifolia | Asteraceae
|
| RADO | Railliardia �dolosa O. Deg. & Sherff | Dubautia dolosa | Asteraceae
|
| RAHE5 | Railliardia herbstobatae (G.D. Carr) St. John | Dubautia herbstobatae | Asteraceae
|
| RAHI2 | Railliardia hillebrandii Mann | Dubautia linearis ssp. hillebrandii | Asteraceae
|
| RAKO | Railliardia kohalae Skottsberg | Dubautia fallax | Asteraceae
|
| RALAH | Railliardia latifolia Gray var. helleri Sherff | Dubautia latifolia | Asteraceae
|
| RALA4 | Railliardia latifolia Gray | Dubautia latifolia | Asteraceae
|
| RALIO | Railliardia linearis Gaud. var. opposita Sherff | Dubautia linearis ssp. opposita | Asteraceae
|
| RALI4 | Railliardia linearis Gaud. | Dubautia linearis ssp. linearis | Asteraceae
|
| RALOS | Railliardia lonchophylla Sherff var. stipitata (Sherff) Sherff | Dubautia scabra ssp. leiophylla | Asteraceae
|
| RAMEA | Railliardia menziesii Gray var. angustifolia Sherff | Dubautia menziesii | Asteraceae
|
| RAME | Railliardia menziesii Gray | Dubautia menziesii | Asteraceae
|
| RAMOO | Railliardia molokaiensis Hbd. var. oppositifolia Sherff | Dubautia molokaiensis | Asteraceae
|
| RAMOS | Railliardia molokaiensis Hbd. var. stipitata Sherff | Dubautia scabra ssp. leiophylla | Asteraceae
|
| RAMO3 | Railliardia molokaiensis Hbd. | Dubautia molokaiensis | Asteraceae
|
| RAMOL | Railliardia montana Mann var. longifolia Sherff | Dubautia reticulata | Asteraceae
|
| RAMOR | Railliardia montana Mann var. robustior Sherff | Dubautia demissifolia | Asteraceae
|
| RAMO4 | Railliardia montana Mann | Dubautia montana | Asteraceae
|
| RAPLL | Railliardia platyphylla Gray var. leptophylla Sherff | Dubautia platyphylla | Asteraceae
|
| RAPLT | Railliardia platyphylla Gray var. trillioidea O. Deg. & Sherff | Dubautia platyphylla | Asteraceae
|
| RAPL3 | Railliardia platyphylla Gray | Dubautia platyphylla | Asteraceae
|
| RARE6 | Railliardia reticulata Sherff | Dubautia reticulata | Asteraceae
|
| RARO | Railliardia rockii Sherff | Dubautia menziesii | Asteraceae
|
| RASCL | Railliardia scabra DC. var. leiophylla Gray | Dubautia scabra ssp. leiophylla | Asteraceae
|
| RASCM2 | Railliardia scabra DC. var. munroi Sherff | Dubautia scabra ssp. leiophylla | Asteraceae
|
| RASHP | Railliardia sherffiana (Fosberg) Sherff var. paucinervia O. Deg. & Sherff | Dubautia sherffiana | Asteraceae
|
| RASH | Railliardia sherffiana (Fosberg) Sherff | Dubautia sherffiana | Asteraceae
|
| RAST2 | Railliardia struthioloides Gray | Dubautia menziesii | Asteraceae
|
| RATE4 | Railliardia ternifolia Sherff | Dubautia thyrsiflora | Asteraceae
|
| RATHC | Railliardia thyrsiflora Sherff var. cernua Sherff | Dubautia thyrsiflora | Asteraceae
|
| RATH | Railliardia thyrsiflora Sherff | Dubautia thyrsiflora | Asteraceae
|
| RAVA | Railliardia �vafra O. Deg. & Sherff | Dubautia linearis ssp. hillebrandii | Asteraceae
|
| RAWA | Railliardia waianapanapaenis (G.D. Carr) St. John | Dubautia dolosa | Asteraceae
|
| RAFA2 | Railliautia �fallax (Sherff) Sherff | Dubautia fallax | Asteraceae
|
| RAFU | Railliautia �fucosa (Sherff) Sherff | Dubautia fallax | Asteraceae
|
| RACU2 | Raimannia curtissii Rose | Oenothera curtissii | Onagraceae
|
| RADR | Raimannia drummondii (Hook.) Rose ex Sprague & Riley | Oenothera drummondii | Onagraceae
|
| RAGR2 | Raimannia grandis (Britt.) Rose | Oenothera grandis | Onagraceae
|
| RAHU | Raimannia humifusa (Nutt.) Rose | Oenothera humifusa | Onagraceae
|
| RALA6 | Raimannia laciniata (Hill) Rose | Oenothera laciniata | Onagraceae
|
| RAMO2 | Raimannia mollissima auct. non (L.) Sprague & Riley | Oenothera humifusa | Onagraceae
|
| RARH3 | Raimannia rhombipetala (Nutt. ex Torr. & Gray) Rose | Oenothera rhombipetala | Onagraceae
|
| RAST | Rainiera stricta (Greene) Greene | false silverback | Asteraceae
|
| RAINI | Rainiera Greene | rainiera | Asteraceae
|
| RACO4 | Rajania cordata L. | himber | Dioscoreaceae
|
| RAOV | Rajania ovata Walt. | Brunnichia ovata | Polygonaceae
|
| RAJAN | Rajania L. | rajania | Dioscoreaceae
|
| RAAH | Ramalina ahtii Kashiw. & T. Nash | cartilage lichen | Ramalinaceae
|
| RAAL60 | Ramalina almquistii Vainio | Almquist's cartilage lichen | Ramalinaceae
|
| RAAM3 | Ramalina americana Hale | American cartilage lichen | Ramalinaceae
|