| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| OLBE | Oligoneuron ×bernardii (Boivin) Nesom | | Asteraceae
|
| OLCA3 | Oligoneuron canescens Rydb. | Oligoneuron rigidum var. humile | Asteraceae
|
| OLCOH | Oligoneuron corymbosum (Ell.) Small var. humile (Porter) Beaudry & Kapoor | Oligoneuron rigidum var. humile | Asteraceae
|
| OLGR3 | Oligoneuron grandiflorum (Raf.) Small | Oligoneuron rigidum var. rigidum | Asteraceae
|
| OLHO | Oligoneuron houghtonii (Torr. & Gray ex Gray) Nesom | Houghton's goldenrod | Asteraceae
|
| OLJA | Oligoneuron jacksonii (Kuntze) Small | Oligoneuron rigidum var. glabratum | Asteraceae
|
| OLKR | Oligoneuron ×krotkovii (Boivin) Nesom | | Asteraceae
|
| OLLU | Oligoneuron ×lutescens (Lindl. ex DC.) Nesom | | Asteraceae
|
| OLNI | Oligoneuron nitidum (Torr. & Gray) Small | shiny goldenrod | Asteraceae
|
| OLOH | Oligoneuron ohioense (Frank ex Riddell) G.N. Jones | Ohio goldenrod | Asteraceae
|
| OLRI2 | Oligoneuron riddellii (Frank ex Riddell) Rydb. | Riddell's goldenrod | Asteraceae
|
| OLRIG | Oligoneuron rigidum (L.) Small var. glabratum (E.L. Braun) Nesom | stiff goldenrod | Asteraceae
|
| OLRIH | Oligoneuron rigidum (L.) Small var. humile (Porter) Nesom | stiff goldenrod | Asteraceae
|
| OLRIR | Oligoneuron rigidum (L.) Small var. rigidum | stiff goldenrod | Asteraceae
|
| OLRI | Oligoneuron rigidum (L.) Small | stiff goldenrod | Asteraceae
|
| OLIGO3 | Oligoneuron Small | goldenrod | Asteraceae
|
| OLCAC | Oligosporus campestris (L.) Cass. ssp. caudatus (Michx.) W.A. Weber | Artemisia campestris ssp. caudata | Asteraceae
|
| OLCAP | Oligosporus campestris (L.) Cass. ssp. pacificus (Nutt.) W.A. Weber | Artemisia campestris ssp. borealis var. scouleriana | Asteraceae
|
| OLCA5 | Oligosporus caudatus Poljakov | Artemisia campestris ssp. caudata | Asteraceae
|
| OLDRD | Oligosporus dracunculus (L.) Poljakov ssp. dracunculinus (S. Wats.) W.A. Weber | Artemisia dracunculus | Asteraceae
|
| OLDRG | Oligosporus dracunculus (L.) Poljakov ssp. glaucus (Pallas ex Willd.) A.& D. Löve | Artemisia dracunculus | Asteraceae
|
| OLDR | Oligosporus dracunculus (L.) Poljakov | Artemisia dracunculus | Asteraceae
|
| OLFI | Oligosporus filifolius (Torr.) W.A. Weber | Artemisia filifolia | Asteraceae
|
| OLGR2 | Oligosporus groenlandicus (Hornem.) A.& D. Löve | Artemisia campestris ssp. borealis var. borealis | Asteraceae
|
| OLPA3 | Oligosporus pacificus (Nutt.) Poljakov | Artemisia campestris ssp. borealis var. scouleriana | Asteraceae
|
| OLPE | Oligosporus pedatifidus (Nutt.) Poljakov | Artemisia pedatifida | Asteraceae
|
| OLAL | Oligotrichum aligerum Mitt. | oligotrichum moss | Polytrichaceae
|
| OLFA70 | Oligotrichum falcatum Steere | sickle oligotrichum moss | Polytrichaceae
|
| OLHE2 | Oligotrichum hercynicum (Hedw.) Lam. & DC. | oligotrichum moss | Polytrichaceae
|
| OLLAC | Oligotrichum laevigatum (Wahlenb.) Bruch & Schimp. in B.S.G. var. cavifolium (Wils.) Frye in Grout | Psilopilum cavifolium | Polytrichaceae
|
| OLLA3 | Oligotrichum laevigatum (Wahlenb.) Bruch & Schimp. in B.S.G. | Psilopilum laevigatum | Polytrichaceae
|
| OLPA2 | Oligotrichum parallelum (Mitt.) Kindb. | oligotrichum moss | Polytrichaceae
|
| OLIGO2 | Oligotrichum Lam. & DC. | oligotrichum moss | Polytrichaceae
|
| OLTE | Olneya tesota Gray | desert ironwood | Fabaceae
|
| OLNEY | Olneya Gray | olneya | Fabaceae
|
| OLDOD | Olsynium douglasii (A. Dietr.) Bickn. var. douglasii | Douglas' grasswidow | Iridaceae
|
| OLDOI | Olsynium douglasii (A. Dietr.) Bickn. var. inflatum (Suksdorf) Cholewa & D. Henderson | inflated grasswidow | Iridaceae
|
| OLDO | Olsynium douglasii (A. Dietr.) Bickn. | Douglas' grasswidow | Iridaceae
|
| OLSYN | Olsynium Raf. | grasswidow | Iridaceae
|
| OLLA | Olyra latifolia L. | carrycillo | Poaceae
|
| OLPA | Olyra pauciflora Sw. | Lithachne pauciflora | Poaceae
|
| OLYRA | Olyra L. | carrycillo | Poaceae
|
| OMSU | Omalotheca supina (L.) DC. | alpine arctic cudweed | Asteraceae
|
| OMSY | Omalotheca sylvatica (L.) Schultz-Bip. & F.W. Schultz | woodland arctic cudweed | Asteraceae
|
| OMALO | Omalotheca Cass. | arctic cudweed | Asteraceae
|
| OMKA | Omphalaria kansana Tuck. | Peccania kansana | Lichinaceae
|
| OMAL2 | Omphalina alpina (Britzelm.) Bresinsky & Stangl | | Tricholomataceae
|
| OMER | Omphalina ericetorum (Pers.:Fr.) M. T. Lange | Omphalina umbellifera | Tricholomataceae
|
| OMHU | Omphalina hudsoniana (H. S. Jenn.) H. E. Bigelow | | Tricholomataceae
|
| OMLU | Omphalina luteovitellina (Pilat & Nannf.) M. T. Lange | Omphalina alpina | Tricholomataceae
|
| OMUM | Omphalina umbellifera (L.:Fr.) Quelet | | Tricholomataceae
|
| OMVE2 | Omphalina velutina (Quelet) Quelet | | Tricholomataceae
|
| OMPHA3 | Omphalina Quelet | omphalina | Tricholomataceae
|
| OMAL | Omphalodes aliena Gray | Mexican navelwort | Boraginaceae
|
| OMLI | Omphalodes linifolia (L.) Moench | whiteflower navelwort | Boraginaceae
|
| OMPHA | Omphalodes P. Mill. | navelwort | Boraginaceae
|
| OMCR | Omphalodiscus crustulosus (Ach.) Schol. | Umbilicaria crustulosa | Umbilicariaceae
|
| OMDE | Omphalodiscus decussatus (Vill.) Schol. | Umbilicaria decussata | Umbilicariaceae
|
| OMKR | Omphalodiscus krascheninnikovii (Savicz) Schol. | Umbilicaria krascheninnikovii | Umbilicariaceae
|
| OMVI | Omphalodiscus virginis (Schaerer) Schol. | Umbilicaria virginis | Umbilicariaceae
|
| OMAR2 | Omphalodium arizonicum (Tuck. ex Willey) Tuck. | Omphalora arizonica | Lecanoraceae
|
| OMAR | Omphalora arizonica (Tuck. ex Willey) T. Nash & Hafellner | | Lecanoraceae
|
| OMPHA2 | Omphalora T. Nash & Hafellner | omphalora | Lecanoraceae
|
| ONAL | Oncidium alatum Cogn. | Oncidium meirax | Orchidaceae
|
| ONAL2 | Oncidium altissimum (Jacq.) Sw. | Wydler's dancing-lady orchid | Orchidaceae
|
| ONBA | Oncidium bahamense Nash ex Britt. & Millsp. | Tolumnia bahamensis | Orchidaceae
|
| ONBA2 | Oncidium baueri auct. non Lindl. | Oncidium altissimum | Orchidaceae
|
| ONCA | Oncidium carthaginense (Jacq.) Sw. | Coot Bay dancing-lady orchid | Orchidaceae
|
| ONEN | Oncidium ensatum Lindl. | Latin American orchid | Orchidaceae
|
| ONFL | Oncidium floridanum Ames | Florida orchid | Orchidaceae
|
| ONLE | Oncidium leiboldii auct. non Reichenb. f. | Tolumnia variegata | Orchidaceae
|
| ONLU | Oncidium luridum auct. non Lindl. | Oncidium undulatum | Orchidaceae
|
| ONME | Oncidium meirax Reichenb. f. | winged-lady orchid | Orchidaceae
|
| ONPR | Oncidium prionochilum Kraenzlin | Tolumnia prionochila | Orchidaceae
|
| ONUN | Oncidium undulatum (Sw.) Salisb. | Cape Sable orchid | Orchidaceae
|
| ONVA | Oncidium variegatum (Sw.) Sw. | Tolumnia variegata | Orchidaceae
|
| ONWY | Oncidium wydleri Reichenb. f. | Oncidium altissimum | Orchidaceae
|
| ONCID | Oncidium Sw. | dancing-lady orchid | Orchidaceae
|
| ONEC2 | Oncoba echinata Oliver | Caloncoba echinata | Flacourtiaceae
|
| ONRO2 | Oncoba routledgei Sprague | | Flacourtiaceae
|
| ONSP3 | Oncoba spinosa Forssk. | | Flacourtiaceae
|
| ONCOB | Oncoba Forsk. | oncoba | Flacourtiaceae
|
| ONAL3 | Oncophorus alpestris (Wahlenb.) Lindb. | Cynodontium alpestre | Dicranaceae
|
| ONGR2 | Oncophorus gracilescens (Web. & Mohr) Lindb. | Cynodontium gracilescens | Dicranaceae
|
| ONJE | Oncophorus jenneri (Schimp. in Howie) Williams | Cynodontium jenneri | Dicranaceae
|
| ONPOS | Oncophorus polycarpus (Hedw.) Brid. var. strumiferus (Hedw.) Brid. | Cynodontium strumiferum | Dicranaceae
|
| ONPO | Oncophorus polycarpus (Hedw.) Brid. | Cynodontium polycarpon | Dicranaceae
|
| ONRA | Oncophorus raui (Aust.) Grout | oncophorus moss | Dicranaceae
|
| ONSC | Oncophorus schisti (Web. & Mohr) Lindb. | Cynodontium schisti | Dicranaceae
|
| ONST3 | Oncophorus strumulosus (C. Müll. & Kindb.) Britt in Williams | Cynodontium alpestre | Dicranaceae
|
| ONTE | Oncophorus tenellus (Bruch & Schimp. in B.S.G.) Williams | Cynodontium tenellum | Dicranaceae
|
| ONVIN | Oncophorus virens (Hedw.) Brid. var. nigrescens Williams in Mac. | Oncophorus virens | Dicranaceae
|
| ONVIS | Oncophorus virens (Hedw.) Brid. var. serratus (Bruch & Schimp. in B.S.G.) Braithw. | Oncophorus virens | Dicranaceae
|
| ONVI4 | Oncophorus virens (Hedw.) Brid. | oncophorus moss | Dicranaceae
|
| ONWAC | Oncophorus wahlenbergii Brid. var. compactus (Bruch & Schimp. in B.S.G.) Braithw. | Oncophorus wahlenbergii | Dicranaceae
|
| ONWAG | Oncophorus wahlenbergii Brid. var. gracilis (Broth.) Arnell & C. Jens. | Oncophorus wahlenbergii | Dicranaceae
|
| ONWA70 | Oncophorus wahlenbergii Brid. | Wahlenberg's oncophorus moss | Dicranaceae
|
| ONCOP | Oncophorus (Brid.) Brid. | oncophorus moss | Dicranaceae
|
| ONPI | Oncosiphon piluliferum (L. f.) Källersjö | stinknet | Asteraceae
|
| ONSU2 | Oncosiphon suffruticosum (L.) Källersjö | shrubby mayweed | Asteraceae
|
| ONCOS | Oncosiphon Källersjö | oncosiphon | Asteraceae
|