| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| STVIC | Stanleya viridiflora Nutt. var. confertiflora B.L. Robins. | Stanleya confertiflora | Brassicaceae
|
| STVI | Stanleya viridiflora Nutt. | green princesplume | Brassicaceae
|
| STANL | Stanleya Nutt. | princesplume | Brassicaceae
|
| STWRT | Stanleyella wrightii (Gray) Rydb. var. tenella (M.E. Jones) Payson | Thelypodium laxiflorum | Brassicaceae
|
| STWR3 | Stanleyella wrightii (Gray) Rydb. | Thelypodium wrightii ssp. wrightii | Brassicaceae
|
| STGI | Stapelia gigantea N.E. Br. | Zulu giant | Asclepiadaceae
|
| STHI7 | Stapelia hirsuta L. | carrion-flower | Asclepiadaceae
|
| STNO | Stapelia nobilis N.E. Br. | Stapelia gigantea | Asclepiadaceae
|
| STVA7 | Stapelia variegata L. | Orbea variegata | Asclepiadaceae
|
| STAPE | Stapelia L. | stapelia | Asclepiadaceae
|
| STCO10 | Stapfia colusana Burtt-Davy | Neostapfia colusana | Poaceae
|
| STBO | Staphylea bolanderi Gray | Sierra bladdernut | Staphyleaceae
|
| STTR | Staphylea trifolia L. | American bladdernut | Staphyleaceae
|
| STAPH | Staphylea L. | bladdernut | Staphyleaceae
|
| STPI4 | Starkea pinnata Nutt. | Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida | Asteraceae
|
| STPE6 | Statice perezii Stapf | Limonium perezii | Plumbaginaceae
|
| STSI6 | Statice sinuata L. | Limonium sinuatum | Plumbaginaceae
|
| STAM5 | Staurothele ambrosiana (A. Massal.) Zschacke | Staurothele drummondii | Verrucariaceae
|
| STAR11 | Staurothele arctica Lynge | arctic wart lichen | Verrucariaceae
|
| STAR15 | Staurothele areolata (Ach.) Lettau | wart lichen | Verrucariaceae
|
| STCA24 | Staurothele catalepta (Ach.) Blomb. & Forss. | wart lichen | Verrucariaceae
|
| STCI9 | Staurothele circinata Tuck. | Staurothele fissa | Verrucariaceae
|
| STCL4 | Staurothele clopima (Wahlenb.) Th. Fr. | Staurothele drummondii | Verrucariaceae
|
| STCL2 | Staurothele clopima sens. Th. Fr. | Staurothele drummondii | Verrucariaceae
|
| STCL3 | Staurothele clopimoides (Arnold) J. Stein | wart lichen | Verrucariaceae
|
| STDI9 | Staurothele diffractella (Nyl.) Tuck. | wart lichen | Verrucariaceae
|
| STDI10 | Staurothele discedens (Nyl.) Zahlbr. | wart lichen | Verrucariaceae
|
| STDR3 | Staurothele drummondii (Tuck.) Tuck. | Drummond's wart lichen | Verrucariaceae
|
| STEF | Staurothele effigurata J. W. Thomson | wart lichen | Verrucariaceae
|
| STEL6 | Staurothele elenkinii Oksner | wart lichen | Verrucariaceae
|
| STFI2 | Staurothele fissa (Taylor) Zwackh | wart lichen | Verrucariaceae
|
| STFU2 | Staurothele fuscocuprea (Nyl.) Zschacke | Staurothele drummondii | Verrucariaceae
|
| STGL6 | Staurothele glacialis Herre | Staurothele fissa | Verrucariaceae
|
| STHA4 | Staurothele hazslinskyi (Korber) Blomb. & Forss. | Staurothele fissa | Verrucariaceae
|
| STHY5 | Staurothele hymenogonia (Nyl.) Th. Fr. | Staurothele discedens | Verrucariaceae
|
| STLE9 | Staurothele lecideoides de Lesd. | wart lichen | Verrucariaceae
|
| STMO6 | Staurothele monicae (Zahlbr.) Wetmore | wart lichen | Verrucariaceae
|
| STOR8 | Staurothele orispruinosa J. W. Thomson | wart lichen | Verrucariaceae
|
| STPE8 | Staurothele perradiata Lynge | Staurothele drummondii | Verrucariaceae
|
| STPO9 | Staurothele polygonia de Lesd. | wart lichen | Verrucariaceae
|
| STRU6 | Staurothele rufa (A. Massal.) Zschacke | Staurothele elenkinii | Verrucariaceae
|
| STRU8 | Staurothele rugosa J. W. Thomson | wart lichen | Verrucariaceae
|
| STRU7 | Staurothele rupifraga (A. Massal.) Arnold | wart lichen | Verrucariaceae
|
| STSE7 | Staurothele sessilis H. Magn. | Staurothele elenkinii | Verrucariaceae
|
| STSU3 | Staurothele succedens (Rehm) Arnold | Staurothele drummondii | Verrucariaceae
|
| STTE7 | Staurothele tenuissima Degel. | wart lichen | Verrucariaceae
|
| STUM3 | Staurothele umbrina (Wahlenb.) Tuck. | Staurothele fissa | Verrucariaceae
|
| STVE6 | Staurothele verruculosa J. W. Thomson | wart lichen | Verrucariaceae
|
| STAUR | Staurothele Norman | wart lichen | Verrucariaceae
|
| STDE7 | Stebbinsoseris decipiens (Nutt.) Chambers, comb. nov. ined. | Santa Cruz silverpuffs | Asteraceae
|
| STHE10 | Stebbinsoseris heterocarpa (Nutt.) Chambers, comb. nov. ined. | grassland silverpuffs | Asteraceae
|
| STEBB2 | Stebbinsoseris gen. nov. ined. | silverpuffs | Asteraceae
|
| STSE9 | Steerecleus serrulatus (Hedw.) Robins. | steerecleus moss | Brachytheciaceae
|
| STEER | Steerecleus Robins. | steerecleus moss | Brachytheciaceae
|
| STCU6 | Stegnosperma cubense A. Rich. | Cuban tangle | Phytolaccaceae
|
| STEGN | Stegnosperma Benth. | stegnosperma | Phytolaccaceae
|
| STLAP | Stegonia latifolia (Schwaegr. in Schultes) Vent. ex Broth. var. pilifera (Brid.) Broth. | Stegonia pilifera | Pottiaceae
|
| STLA70 | Stegonia latifolia (Schwaegr. in Schultes) Vent. ex Broth. | wideleaf stegonia moss | Pottiaceae
|
| STPI9 | Stegonia pilifera (Brid.) Crum & Anderson | stegonia moss | Pottiaceae
|
| STEGO | Stegonia Vent. | stegonia moss | Pottiaceae
|
| STHI3 | Steinchisma hians (Ell.) Nash | gaping grass | Poaceae
|
| STEIN | Steinchisma Raf. | gaping grass | Poaceae
|
| STGE3 | Steinia geophana (Nyl.) Stein | | Lecideaceae
|
| STEIN2 | Steinia Korber | steinia | Lecideaceae
|
| STCI8 | Steironema ciliatum (L.) Baudo | Lysimachia ciliata | Primulaceae
|
| STGR10 | Steironema gramineum Greene | Lysimachia graminea | Primulaceae
|
| STHE7 | Steironema heterophyllum (Michx.) Baudo | Lysimachia lanceolata | Primulaceae
|
| STHY7 | Steironema hybridum (Michx.) Raf. ex B.D. Jackson | Lysimachia hybrida | Primulaceae
|
| STIN6 | Steironema intermedium Kearney | Lysimachia tonsa | Primulaceae
|
| STLA12 | Steironema laevigatum T.J. Howell | Lysimachia hybrida | Primulaceae
|
| STLAH | Steironema lanceolatum (Walt.) Gray var. hybridum (Michx.) Gray | Lysimachia hybrida | Primulaceae
|
| STLA13 | Steironema lanceolatum (Walt.) Gray | Lysimachia lanceolata | Primulaceae
|
| STPU5 | Steironema pumilum Greene | Lysimachia ciliata | Primulaceae
|
| STQU | Steironema quadriflorum (Sims) A.S. Hitchc. | Lysimachia quadriflora | Primulaceae
|
| STRA | Steironema radicans (Hook.) Gray | Lysimachia radicans | Primulaceae
|
| STTO5 | Steironema tonsum (Wood) Bickn. ex Britt. | Lysimachia tonsa | Primulaceae
|
| STBU2 | Stelechocarpus burahol (Blume) Hook. f. & Thomson | burahol | Annonaceae
|
| STELE | Stelechocarpus (Blume) Hook. & Thomson | stelechocarpus | Annonaceae
|
| STPE | Stelis perpusilliflora Cogn. | West Indian leach orchid | Orchidaceae
|
| STPY2 | Stelis pygmaea Cogn. | pygmy leach orchid | Orchidaceae
|
| STELI | Stelis Sw. | leach orchid | Orchidaceae
|
| STAL3 | Stellaria alaskana Hult�n | Alaska starwort | Caryophyllaceae
|
| STAL4 | Stellaria alsine Grimm | bog chickweed | Caryophyllaceae
|
| STAM | Stellaria americana (Porter ex B.L. Robins.) Standl. | American chickweed | Caryophyllaceae
|
| STAN2 | Stellaria antillana Urban | West Indian starwort | Caryophyllaceae
|
| STAP3 | Stellaria apetala Ucria ex Roemer | Stellaria media ssp. media | Caryophyllaceae
|
| STAP2 | Stellaria apetala auct. non Ucria ex Roemer | Stellaria media ssp. pallida | Caryophyllaceae
|
| STAQ4 | Stellaria aquatica (L.) Scop. | Myosoton aquaticum | Caryophyllaceae
|
| STAT | Stellaria atrata (J.W. Moore) Boivin | Stellaria longifolia var. atrata | Caryophyllaceae
|
| STBI7 | Stellaria biflora L. | Minuartia biflora | Caryophyllaceae
|
| STBOB2 | Stellaria borealis Bigelow ssp. bongardiana (Fern.) Piper & Beattie | Stellaria borealis ssp. sitchana | Caryophyllaceae
|
| STBOB | Stellaria borealis Bigelow ssp. borealis | boreal starwort | Caryophyllaceae
|
| STBOS | Stellaria borealis Bigelow ssp. sitchana (Steud.) Piper | Sitka starwort | Caryophyllaceae
|
| STBOB3 | Stellaria borealis Bigelow var. bongardiana Fern. | Stellaria borealis ssp. sitchana | Caryophyllaceae
|
| STBOC | Stellaria borealis Bigelow var. crispa (Cham. & Schlecht.) Fenzl ex Torr. & Gray | Stellaria crispa | Caryophyllaceae
|
| STBOF | Stellaria borealis Bigelow var. floribunda Fern. | Stellaria borealis ssp. borealis | Caryophyllaceae
|
| STBOI | Stellaria borealis Bigelow var. isophylla Fern. | Stellaria borealis ssp. borealis | Caryophyllaceae
|
| STBOS3 | Stellaria borealis Bigelow var. simcoei (T.J. Howell) Fern. | Stellaria calycantha | Caryophyllaceae
|
| STBOS2 | Stellaria borealis Bigelow var. sitchana (Steud.) Fern. | Stellaria borealis ssp. sitchana | Caryophyllaceae
|
| STBO3 | Stellaria borealis Bigelow | boreal starwort | Caryophyllaceae
|
| STBRB3 | Stellaria brachypetala Bong. var. bongardiana Fern. | Stellaria borealis ssp. sitchana | Caryophyllaceae
|