| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| ONVE | Oncostema verna (Hudson) Speta | sea-onion | Liliaceae
|
| ONCOS2 | Oncostema Rafin. | oncostema | Liliaceae
|
| ONPA2 | Oncostylis pauciflora Liebm. | Bulbostylis pauciflora | Cyperaceae
|
| ONGO | Ongokea gore (Hua) Pierre | boleko nut | Olacaceae
|
| ONKL | Ongokea klaineana Pierre | Ongokea gore | Olacaceae
|
| ONGOK | Ongokea Pierre | ongokea | Olacaceae
|
| ONSA | Onobrychis sativa Lam. | Onobrychis viciifolia | Fabaceae
|
| ONVI3 | Onobrychis viciaefolia Scop. | Onobrychis viciifolia | Fabaceae
|
| ONVI | Onobrychis viciifolia Scop. | sainfoin | Fabaceae
|
| ONOBR | Onobrychis P. Mill. | sainfoin | Fabaceae
|
| ONSE | Onoclea sensibilis L. | sensitive fern | Dryopteridaceae
|
| ONSTP | Onoclea struthiopteris (L.) Hoffmann var. pensylvanica (Willd.) Boivin | Matteuccia struthiopteris | Dryopteridaceae
|
| ONST2 | Onoclea struthiopteris (L.) Hoffmann p.p. | Matteuccia struthiopteris | Dryopteridaceae
|
| ONOCL | Onoclea L. | sensitive fern | Dryopteridaceae
|
| ONAL5 | Ononis alopecuroides L. | foxtail restharrow | Fabaceae
|
| ONAR | Ononis arvensis L. | field restharrow | Fabaceae
|
| ONCA2 | Ononis campestris G. Koch & Ziz | spiny restharrow | Fabaceae
|
| ONRE | Ononis repens L. | common restharrow | Fabaceae
|
| ONSP | Ononis spinosa L. | Ononis campestris | Fabaceae
|
| ONONI | Ononis L. | restharrow | Fabaceae
|
| ONAC | Onopordum acanthium L. | Scotch cottonthistle | Asteraceae
|
| ONIL | Onopordum illyricum L. | Illyrian cottonthistle | Asteraceae
|
| ONTA | Onopordum tauricum Willd. | bull cottonthistle | Asteraceae
|
| ONOPO | Onopordum L. | cottonthistle | Asteraceae
|
| ONEC | Onosma echioides L. | onosma | Boraginaceae
|
| ONOSM2 | Onosma L. | onosma | Boraginaceae
|
| ONBEH | Onosmodium bejariense DC. ex A. DC. var. hispidissimum (Mackenzie) B.L. Turner | Onosmodium molle ssp. hispidissimum | Boraginaceae
|
| ONBEO | Onosmodium bejariense DC. ex A. DC. var. occidentale (Mackenzie) B.L. Turner | Onosmodium molle ssp. occidentale | Boraginaceae
|
| ONBES | Onosmodium bejariense DC. ex A. DC. var. subsetosum (Mackenzie & Bush) B.L. Turner | Onosmodium molle ssp. subsetosum | Boraginaceae
|
| ONBE | Onosmodium bejariense DC. ex A. DC. | Onosmodium molle ssp. bejariense | Boraginaceae
|
| ONHE | Onosmodium helleri Small | Heller's marbleseed | Boraginaceae
|
| ONHIM | Onosmodium hispidissimum Mackenzie var. macrospermum Mackenzie & Bush | Onosmodium molle ssp. hispidissimum | Boraginaceae
|
| ONHI | Onosmodium hispidissimum Mackenzie | Onosmodium molle ssp. hispidissimum | Boraginaceae
|
| ONMOB3 | Onosmodium molle Michx. ssp. bejariense (DC. ex A. DC.) Cochrane | softhair marbleseed | Boraginaceae
|
| ONMOH2 | Onosmodium molle Michx. ssp. hispidissimum (Mackenzie) Boivin | softhair marbleseed | Boraginaceae
|
| ONMOM | Onosmodium molle Michx. ssp. molle | softhair marbleseed | Boraginaceae
|
| ONMOO2 | Onosmodium molle Michx. ssp. occidentale (Mackenzie) Cochrane | western marbleseed | Boraginaceae
|
| ONMOS | Onosmodium molle Michx. ssp. subsetosum (Mackenzie & Bush) Cochrane | softhair marbleseed | Boraginaceae
|
| ONMOB2 | Onosmodium molle Michx. var. bejariense (DC. ex A. DC.) Cronq. | Onosmodium molle ssp. bejariense | Boraginaceae
|
| ONMOH | Onosmodium molle Michx. var. hispidissimum (Mackenzie) Cronq. | Onosmodium molle ssp. hispidissimum | Boraginaceae
|
| ONMOO | Onosmodium molle Michx. var. occidentale (Mackenzie) I.M. Johnston | Onosmodium molle ssp. occidentale | Boraginaceae
|
| ONMOS2 | Onosmodium molle Michx. var. subsetosum (Mackenzie & Bush) Cronq. | Onosmodium molle ssp. subsetosum | Boraginaceae
|
| ONMO | Onosmodium molle Michx. | softhair marbleseed | Boraginaceae
|
| ONOCS | Onosmodium occidentale Mackenzie var. sylvestre Mackenzie | Onosmodium molle ssp. occidentale | Boraginaceae
|
| ONOC | Onosmodium occidentale Mackenzie | Onosmodium molle ssp. occidentale | Boraginaceae
|
| ONSU | Onosmodium subsetosum Mackenzie & Bush | Onosmodium molle ssp. subsetosum | Boraginaceae
|
| ONVIH | Onosmodium virginianum (L.) A. DC. var. hirsutum Mackenzie | Onosmodium virginianum | Boraginaceae
|
| ONVI2 | Onosmodium virginianum (L.) A. DC. | wild Job's tears | Boraginaceae
|
| ONOSM | Onosmodium Michx. | marbleseed | Boraginaceae
|
| ONDE | Onychium densum Brack. | Aspidotis densa | Pteridaceae
|
| ONST | Onychium strictum auct. non Kunze | Anopteris hexagona ssp. intermedia | Pteridaceae
|
| OOEN | Oonopsis engelmannii (Gray) Greene | Engelmann's false goldenweed | Asteraceae
|
| OOFOF | Oonopsis foliosa (Gray) Greene var. foliosa | leafy false goldenweed | Asteraceae
|
| OOFOM | Oonopsis foliosa (Gray) Greene var. monocephala (A. Nels.) Kartesz & Gandhi | Raven Ridge false goldenweed | Asteraceae
|
| OOFO | Oonopsis foliosa (Gray) Greene | leafy false goldenweed | Asteraceae
|
| OOMU | Oonopsis multicaulis (Nutt.) Greene | branched false goldenweed | Asteraceae
|
| OOWA | Oonopsis wardii (Gray) Greene | Ward's false goldenweed | Asteraceae
|
| OONOP | Oonopsis Nutt. | false goldenweed | Asteraceae
|
| OPAG2 | Opegrapha agelaea Fee | scribble lichen | Opegraphaceae
|
| OPAS | Opegrapha astraea Tuck. | scribble lichen | Opegraphaceae
|
| OPAT3 | Opegrapha atra Pers. | scribble lichen | Opegraphaceae
|
| OPAU9 | Opegrapha aurantiaca de Lesd. | scribble lichen | Opegraphaceae
|
| OPBE2 | Opegrapha betulina Sm. | Opegrapha herbarum | Opegraphaceae
|
| OPBO2 | Opegrapha bonplandii Fee | Bonpland's scribble lichen | Opegraphaceae
|
| OPCA9 | Opegrapha calcarea Turner ex Sm. & Sowerby | calcareous scribble lichen | Opegraphaceae
|
| OPCA10 | Opegrapha candida Mull. Arg. | scribble lichen | Opegraphaceae
|
| OPCI | Opegrapha cinerea Chevall. | Opegrapha vulgata | Opegraphaceae
|
| OPCY2 | Opegrapha cypressi R. C. Harris | scribble lichen | Opegraphaceae
|
| OPDI6 | Opegrapha diaphora (Ach.) Ach. | Opegrapha varia | Opegraphaceae
|
| OPDI7 | Opegrapha diaphoroides Nyl. | Lecanographa grumulosa | Uncertain Lichen Family
|
| OPFI2 | Opegrapha filicina Mont. | scribble lichen | Opegraphaceae
|
| OPGL | Opegrapha glaucomaria (Nyl.) Kallsten | scribble lichen | Opegraphaceae
|
| OPGY | Opegrapha gyrocarpa Flotow | scribble lichen | Opegraphaceae
|
| OPHA | Opegrapha hassei Zahlbr. | Hasse's scribble lichen | Opegraphaceae
|
| OPHE2 | Opegrapha herbarum Mont. | scribble lichen | Opegraphaceae
|
| OPHE3 | Opegrapha herpetica Ach. | Opegrapha rufescens | Opegraphaceae
|
| OPHY3 | Opegrapha hypothallina (Zahlbr.) Tehler | Lecanographa hypothallina | Uncertain Lichen Family
|
| OPLA5 | Opegrapha lamyi (O. J. Rich. ex Nyl.) Triebel | scribble lichen | Opegraphaceae
|
| OPLE4 | Opegrapha leucoplaca Mull. Arg. | scribble lichen | Opegraphaceae
|
| OPLI6 | Opegrapha lichenoides Pers. | Opegrapha varia | Opegraphaceae
|
| OPLI5 | Opegrapha lithryga Ach. | scribble lichen | Opegraphaceae
|
| OPLO2 | Opegrapha longissima Mull. Arg. | scribble lichen | Opegraphaceae
|
| OPMI3 | Opegrapha microcycla Tuck. | scribble lichen | Opegraphaceae
|
| OPNI3 | Opegrapha niveoatra (Borrer) J. R. Laundon | scribble lichen | Opegraphaceae
|
| OPOC4 | Opegrapha ochrocheila Nyl. | scribble lichen | Opegraphaceae
|
| OPPR4 | Opegrapha prosiliens Stirton | Opegrapha protuberans | Opegraphaceae
|
| OPPR2 | Opegrapha prosodea Ach. | scribble lichen | Opegraphaceae
|
| OPPR3 | Opegrapha protuberans Zahlbr. | scribble lichen | Opegraphaceae
|
| OPPU4 | Opegrapha pulicaris auct. | Opegrapha varia | Opegraphaceae
|
| OPPU5 | Opegrapha pulvinata Rehm | scribble lichen | Opegraphaceae
|
| OPQU | Opegrapha quaternella Nyl. | scribble lichen | Opegraphaceae
|
| OPRA3 | Opegrapha ravenelii (Tuck.) Tehler | scribble lichen | Opegraphaceae
|
| OPRI | Opegrapha rimalis Pers. ex Ach. | Opegrapha varia | Opegraphaceae
|
| OPRU7 | Opegrapha rufescens Pers. | scribble lichen | Opegraphaceae
|
| OPRU8 | Opegrapha rupestris Pers. | scribble lichen | Opegraphaceae
|
| OPSA2 | Opegrapha saxicola Ach. | Opegrapha rupestris | Opegraphaceae
|
| OPSO | Opegrapha sorediifera P. James | scribble lichen | Opegraphaceae
|
| OPSP8 | Opegrapha sphaerophoricola Isbrand & Alstrup | scribble lichen | Opegraphaceae
|
| OPST6 | Opegrapha staurothelicola (Fink) | scribble lichen | Opegraphaceae
|
| OPUM | Opegrapha umbellulariae Zahlbr. | umbel scribble lichen | Opegraphaceae
|
| OPVA2 | Opegrapha varia Pers. | scribble lichen | Opegraphaceae
|