- Photo: Ochna serrulata 10.
- Photo: Ochna serrulata 2.
- Photo: Ochna serrulata 4.
- Photo: Ochna serrulata 5.
- Photo: Ochna serrulata 6.
- Photo: Ochna serrulata 7.
- Photo: Ochna serrulata 8.
- Photo: Ochna serrulata 9.
- Photo: Ocimum americanum 1.
- Photo: Ocimum americanum.
- Photo: Ocimum basilicum 2.
- Photo: Ocimum basilicum 3.
- Photo: Ocimum basilicum 4.
- Photo: Ocimum basilicum 7.
- Photo: Ocimum gratissimum 1.
- Photo: Ocimum gratissimum.
- Photo: Ocimum minimum 1.
- Photo: Ocimum minimum.
- Photo: Ocimum tenuiflorum.
- Photo: Odontites litoralis.
- Photo: Odontites vulgaris 1.
- Photo: Odontites vulgaris.
- Photo: Oenanthe pimpinelloides.
- Photo: Oenothera 1.
- Photo: Oenothera biennis 1.
- Photo: Oenothera biennis 10.
- Photo: Oenothera biennis 11.
- Photo: Oenothera biennis 12.
- Photo: Oenothera biennis 13.
- Photo: Oenothera biennis 3.
- Photo: Oenothera biennis 4.
- Photo: Oenothera biennis 5.
- Photo: Oenothera biennis 6.
- Photo: Oenothera biennis 7.
- Photo: Oenothera biennis 8.
- Photo: Oenothera biennis 9.
- Photo: Oenothera biennis.
- Photo: Oenothera deltoides 1.
- Photo: Oenothera deltoides.
- Photo: Oenothera flava.
- Photo: Oenothera fruticosa 1.
- Photo: Oenothera fruticosa 2.
- Photo: Oenothera fruticosa 3.
- Photo: Oenothera fruticosa.
- Photo: Oenothera macrocarpa 1.
- Photo: Oenothera macrocarpa 10.
- Photo: Oenothera macrocarpa 2.
- Photo: Oenothera macrocarpa 3.
- Photo: Oenothera macrocarpa 4.
- Photo: Oenothera macrocarpa 5.
- Photo: Oenothera macrocarpa 6.
- Photo: Oenothera macrocarpa 7.
- Photo: Oenothera macrocarpa 8.
- Photo: Oenothera macrocarpa 9.
- Photo: Oenothera macrocarpa.
- Photo: Oenothera rosea 1.
- Photo: Oenothera rosea.
- Photo: Oenothera speciosa 1.
- Photo: Oenothera speciosa.
- Photo: Oenothera villosa 1.
- Photo: Oenothera villosa.
- Photo: Oenothera.
- Photo: Omphalodes verna.
- Photo: Oncidium 1.
- Photo: Oncidium 2.
- Photo: Oncidium.
- Photo: Onobrychis viciifolia 1.
- Photo: Onobrychis viciifolia 2.
- Photo: Onobrychis viciifolia.
- Photo: Onoclea orientalis 1.
- Photo: Onoclea orientalis.
- Photo: Onoclea sensibilis 1.
- Photo: Onoclea sensibilis 2.
- Photo: Onoclea sensibilis 3.
- Photo: Onoclea sensibilis.
- Photo: Ononis 1.
- Photo: Ononis repens 1.
- Photo: Ononis repens 2.
- Photo: Ononis repens 3.
- Photo: Ononis repens.
- Photo: Ononis spinosa 1.
- Photo: Ononis spinosa.
- Photo: Ononis.
- Photo: Onopordum acanthium 1.
- Photo: Onopordum acanthium 2.
- Photo: Onopordum acanthium 3.
- Photo: Onopordum acanthium 4.
- Photo: Onopordum acanthium 5.
- Photo: Onopordum acanthium.
- Photo: Onoseris hastata.
- Photo: Onosma alborosea 1.
- Photo: Onosma alborosea.
- Photo: Ophioglossum vulgatum 1.
- Photo: Ophioglossum vulgatum.
- Photo: Oplopanax horridus 1.
- Photo: Oplopanax horridus 2.
- Photo: Oplopanax horridus 3.
- Photo: Oplopanax horridus 4.
- Photo: Oplopanax horridus 5.
- Photo: Oplopanax horridus 6.
- Photo: Oplopanax horridus.
- Photo: Opuntia bigelovii.
- Photo: Opuntia engelmannii.
- Photo: Opuntia ficus indica.
- Photo: Opuntia fulgida 1.
- Photo: Opuntia fulgida 2.
- Photo: Opuntia fulgida.
- Photo: Opuntia imbricata.
- Photo: Opuntia kleiniae.
- Photo: Opuntia leptocaulis 1.
- Photo: Opuntia leptocaulis.
- Photo: Opuntia microdasys.
- Photo: Opuntia spinosior 1.
- Photo: Opuntia spinosior.
- Photo: Opuntia.
- Photo: Origanum dictamnus 1.
- Photo: Origanum dictamnus 2.
- Photo: Origanum dictamnus 3.
- Photo: Origanum dictamnus 4.
- Photo: Origanum dictamnus.
- Photo: Origanum heracleoticum 1.
- Photo: Origanum heracleoticum.
- Photo: Origanum majorana 1.
- Photo: Origanum majorana 2.
- Photo: Origanum majorana 3.
- Photo: Origanum majorana 4.
- Photo: Origanum majorana.
- Photo: Origanum rotundifolium.
- Photo: Origanum vulgare 1.
- Photo: Origanum vulgare 2.
- Photo: Origanum vulgare 3.
- Photo: Origanum vulgare 4.
- Photo: Origanum vulgare 5.
- Photo: Origanum vulgare 6.
- Photo: Origanum vulgare 7.
- Photo: Origanum vulgare.
- Photo: Orobanche caryophyllacea 1.
- Photo: Orobanche caryophyllacea.
- Photo: Orobanche cooperi.
- Photo: Orobanche gracilis.
- Photo: Orobanche lucorum.
- Photo: Orthilia secunda 1.
- Photo: Orthilia secunda.
- Photo: Orychophragmus violaceus.
- Photo: Oryza sativa 1.
- Photo: Oryza sativa 2.
- Photo: Oryza sativa 3.
- Photo: Oryza sativa 4.
- Photo: Oryza sativa.
- Photo: Osmorhiza 1.
- Photo: Osmorhiza.
- Photo: Osmunda cinnamomea 1.
- Photo: Osmunda cinnamomea 2.
- Photo: Osmunda cinnamomea 3.
- Photo: Osmunda cinnamomea.
- Photo: Osmunda claytoniana 1.
- Photo: Osmunda claytoniana.
- Photo: Osmunda lancea 1.
- Photo: Osmunda lancea 2.
- Photo: Osmunda lancea.
- Photo: Osmunda regalis 1.
- Photo: Osmunda regalis.
- Photo: Osteospermum 1.
- Photo: Osteospermum 2.
- Photo: Osteospermum barberiae 1.
- Photo: Osteospermum barberiae.
- Photo: Osteospermum jucundum 1.
- Photo: Osteospermum jucundum 2.
- Photo: Osteospermum jucundum 3.
- Photo: Osteospermum jucundum 4.
- Photo: Osteospermum jucundum.
- Photo: Osteospermum.
- Photo: Ostrya carpinifolia 1.
- Photo: Ostrya carpinifolia.
- Photo: Oxalis acetosella 1.
- Photo: Oxalis acetosella 2.
- Photo: Oxalis acetosella 3.
- Photo: Oxalis acetosella.
- Photo: Oxalis corniculata.
- Photo: Oxalis.
- Photo: Oxyria digyna 1.
- Photo: Oxyria digyna 2.
- Photo: Oxyria digyna 3.
- Photo: Oxyria digyna 4.
- Photo: Oxyria digyna.
O
The Os.