| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| SIPHO | Siphonoglossa Oerst. | tubetongue | Acanthaceae
|
| SIAM3 | Siphonychia americana (Nutt.) Torr. & Gray | Paronychia americana ssp. americana | Caryophyllaceae
|
| SIDI7 | Siphonychia diffusa Chapman | Paronychia patula | Caryophyllaceae
|
| SIER3 | Siphonychia erecta Chapman | Paronychia erecta var. erecta | Caryophyllaceae
|
| SIIN12 | Siphonychia interior (Small) Core | Paronychia rugelii var. interior | Caryophyllaceae
|
| SIPA7 | Siphonychia pauciflora Small | Paronychia americana ssp. pauciflora | Caryophyllaceae
|
| SIRU5 | Siphonychia rugellii Chapman | Paronychia rugelii var. rugelii | Caryophyllaceae
|
| SICE60 | Siphula ceratites (Wahlenb.) Fr. | whitefingers lichen | Uncertain Lichen Family
|
| SIDA2 | Siphula dactyliza Nyl. | whitefingers lichen | Uncertain Lichen Family
|
| SISI3 | Siphula simplex (Taylor) Nyl. | Siphula ceratites | Uncertain Lichen Family
|
| SIPHU2 | Siphula Fr. | whitefingers lichen | Uncertain Lichen Family
|
| SIAL11 | Sisymbrium alliaria (L.) Scop. | Alliaria petiolata | Brassicaceae
|
| SIAL2 | Sisymbrium altissimum L. | tall tumblemustard | Brassicaceae
|
| SIAM4 | Sisymbrium ambiguum (S. Wats.) Payson | Thelypodiopsis ambigua var. ambigua | Brassicaceae
|
| SIAM5 | Sisymbrium amphibium L. | Rorippa amphibia | Brassicaceae
|
| SIAU4 | Sisymbrium aureum (Eastw.) Payson | Thelypodiopsis aurea | Brassicaceae
|
| SIAU2 | Sisymbrium auriculatum Gray | eared hedgemustard | Brassicaceae
|
| SIAU6 | Sisymbrium austriacum Jacq. | jeweled rocket | Brassicaceae
|
| SIBR5 | Sisymbrium brachycarpum Richards. | Descurainia pinnata ssp. brachycarpa | Brassicaceae
|
| SICU5 | Sisymbrium curvisiliqua Hook. | Rorippa curvisiliqua var. curvisiliqua | Brassicaceae
|
| SIDE7 | Sisymbrium dentatum Torr. | Arabis shortii | Brassicaceae
|
| SIELJ | Sisymbrium elegans (M.E. Jones) Payson var. juniperorum (Payson) Harrington | Thelypodiopsis juniperorum | Brassicaceae
|
| SIEL5 | Sisymbrium elegans (M.E. Jones) Payson | Thelypodiopsis elegans | Brassicaceae
|
| SIER5 | Sisymbrium erysimoides Desf. | Mediterranean rocket | Brassicaceae
|
| SIHU2 | Sisymbrium humile C.A. Mey. | Braya humilis | Brassicaceae
|
| SIIN11 | Sisymbrium incanum Bernh. ex Fisch. & C.A. Mey. | Descurainia incana ssp. incana | Brassicaceae
|
| SIINF | Sisymbrium incisum Engelm. var. filipes Gray | Descurainia pinnata ssp. filipes | Brassicaceae
|
| SIIN6 | Sisymbrium incisum Engelm. | Descurainia incana ssp. incisa | Brassicaceae
|
| SIIN9 | Sisymbrium indicum L. | Rorippa indica var. indica | Brassicaceae
|
| SIIR | Sisymbrium irio L. | London rocket | Brassicaceae
|
| SIJU3 | Sisymbrium juniperorum Payson | Thelypodiopsis juniperorum | Brassicaceae
|
| SIKE2 | Sisymbrium kearneyi Rollins | Thelypodiopsis purpusii | Brassicaceae
|
| SILI7 | Sisymbrium linearifolium (Gray) Payson | Schoenocrambe linearifolia | Brassicaceae
|
| SILI5 | Sisymbrium linifolium (Nutt.) Nutt. ex Torr. & Gray | Schoenocrambe linifolia | Brassicaceae
|
| SILO3 | Sisymbrium loeselii L. | small tumbleweed mustard | Brassicaceae
|
| SILO9 | Sisymbrium longipedicellatum Fourn. | Descurainia pinnata ssp. filipes | Brassicaceae
|
| SIMI7 | Sisymbrium microtites B.L. Robins. | Rorippa microtitis | Brassicaceae
|
| SIMU6 | Sisymbrium murale L. | Diplotaxis muralis | Brassicaceae
|
| SINA4 | Sisymbrium nasturtium-aquaticum L. | Rorippa nasturtium-aquaticum | Brassicaceae
|
| SIOFL | Sisymbrium officinale (L.) Scop. var. leiocarpum DC. | Sisymbrium officinale | Brassicaceae
|
| SIOF | Sisymbrium officinale (L.) Scop. | hedgemustard | Brassicaceae
|
| SIOR4 | Sisymbrium orientale L. | Indian hedgemustard | Brassicaceae
|
| SIPI3 | Sisymbrium pinnatum (Walt.) Greene | Descurainia pinnata ssp. pinnata | Brassicaceae
|
| SIPO2 | Sisymbrium polyceratium L. | shortfruit hedgemustard | Brassicaceae
|
| SIPU4 | Sisymbrium purpusii (Brandeg.) O.E. Schulz | Thelypodiopsis purpusii | Brassicaceae
|
| SISA7 | Sisymbrium salsugineum Pallas | Arabidopsis salsuginea | Brassicaceae
|
| SISH3 | Sisymbrium shinnersii M.C. Johnston | Thelypodiopsis shinnersii | Brassicaceae
|
| SISO4 | Sisymbrium sophia L. | Descurainia sophia | Brassicaceae
|
| SISO5 | Sisymbrium sophioides Fisch. ex Hook. | Descurainia sophioides | Brassicaceae
|
| SITE5 | Sisymbrium tenuifolium L. | Diplotaxis tenuifolia | Brassicaceae
|
| SITH3 | Sisymbrium thalianum (L.) J. Gay & Monn. | Arabidopsis thaliana | Brassicaceae
|
| SITU2 | Sisymbrium turczaninowii Sonder | Russian rocket | Brassicaceae
|
| SIVA4 | Sisymbrium vaseyi S. Wats. ex B.L. Robins. | Thelypodiopsis vaseyi | Brassicaceae
|
| SIVE3 | Sisymbrium vernale (Woot. & Standl.) O.E. Schulz | Thelypodiopsis purpusii | Brassicaceae
|
| SIVI7 | Sisymbrium virgatum Nutt. | Halimolobos virgata | Brassicaceae
|
| SIVI9 | Sisymbrium viscosum (Rydb.) Blank. | Descurainia incana ssp. viscosa | Brassicaceae
|
| SISYM | Sisymbrium L. | hedgemustard | Brassicaceae
|
| SIAC2 | Sisyrinchium acre Mann | Hawai'i blue-eyed grass | Iridaceae
|
| SIAL3 | Sisyrinchium albidum Raf. | white blue-eyed grass | Iridaceae
|
| SIAN3 | Sisyrinchium angustifolium P. Mill. | narrowleaf blue-eyed grass | Iridaceae
|
| SIAP2 | Sisyrinchium apiculatum Bickn. | Sisyrinchium atlanticum | Iridaceae
|
| SIAR2 | Sisyrinchium arenicola Bickn. | Sisyrinchium fuscatum | Iridaceae
|
| SIAR3 | Sisyrinchium arizonicum Rothrock | Arizona blue-eyed grass | Iridaceae
|
| SIAS3 | Sisyrinchium asheianum Bickn. | Sisyrinchium albidum | Iridaceae
|
| SIAT | Sisyrinchium atlanticum Bickn. | eastern blue-eyed grass | Iridaceae
|
| SIBE | Sisyrinchium bellum S. Wats. | western blue-eyed grass | Iridaceae
|
| SIBEC | Sisyrinchium bermudiana L. var. crebrum (Fern.) Boivin | Sisyrinchium montanum var. crebrum | Iridaceae
|
| SIBE3 | Sisyrinchium bermudiana auct. non L. | Sisyrinchium angustifolium | Iridaceae
|
| SIBI | Sisyrinchium biforme Bickn. | wiry blue-eyed grass | Iridaceae
|
| SIBI2 | Sisyrinchium birameum Piper | Sisyrinchium idahoense var. idahoense | Iridaceae
|
| SIBO | Sisyrinchium boreale (Bickn.) Henry | Sisyrinchium californicum | Iridaceae
|
| SIBR6 | Sisyrinchium brayi Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SIBR4 | Sisyrinchium brownei Small | Sisyrinchium rosulatum | Iridaceae
|
| SIBU | Sisyrinchium bulbosum P. Mill. | Eleutherine bulbosa | Iridaceae
|
| SICA8 | Sisyrinchium californicum (Ker-Gawl. ex Sims) Ait. | golden blue-eyed grass | Iridaceae
|
| SICAK | Sisyrinchium campestre Bickn. var. kansanum Bickn. | Sisyrinchium campestre | Iridaceae
|
| SICA9 | Sisyrinchium campestre Bickn. | prairie blue-eyed grass | Iridaceae
|
| SICA19 | Sisyrinchium canbyi Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SICA11 | Sisyrinchium capillare Bickn. | | Iridaceae
|
| SICA18 | Sisyrinchium carolinianum Bickn. | Sisyrinchium nashii | Iridaceae
|
| SICE | Sisyrinchium cernuum (Bickn.) Kearney | nodding blue-eyed grass | Iridaceae
|
| SICH2 | Sisyrinchium chilense Hook. | swordleaf blue-eyed grass | Iridaceae
|
| SICO8 | Sisyrinchium colubriferum Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SIDEA2 | Sisyrinchium demissum Greene var. amethystinum (Bickn.) Kearney & Peebles | Sisyrinchium demissum | Iridaceae
|
| SIDE4 | Sisyrinchium demissum Greene | stiff blue-eyed grass | Iridaceae
|
| SIDI5 | Sisyrinchium dichotomum Bickn. | wishbone blue-eyed grass | Iridaceae
|
| SIDI3 | Sisyrinchium dimorphum R. Oliver | Sisyrinchium biforme | Iridaceae
|
| SIDOI | Sisyrinchium douglasii A. Dietr. var. inflatum (Suksdorf) P. Holmgren | Olsynium douglasii var. inflatum | Iridaceae
|
| SIDO2 | Sisyrinchium douglasii A. Dietr. | Olsynium douglasii var. douglasii | Iridaceae
|
| SIEA | Sisyrinchium eastwoodiae Bickn. | Sisyrinchium bellum | Iridaceae
|
| SIEL3 | Sisyrinchium elmeri Greene | Elmer's blue-eyed grass | Iridaceae
|
| SIEN | Sisyrinchium ensigerum Bickn. | Sisyrinchium chilense | Iridaceae
|
| SIEX2 | Sisyrinchium exile Bickn. | Sisyrinchium rosulatum | Iridaceae
|
| SIFA2 | Sisyrinchium farwellii Bickn. | Farwell's blue-eyed grass | Iridaceae
|
| SIFI6 | Sisyrinchium fibrosum Bickn. | Sisyrinchium nashii | Iridaceae
|
| SIFL3 | Sisyrinchium flaviflorum Bickn. | Sisyrinchium campestre | Iridaceae
|
| SIFL4 | Sisyrinchium floridanum Bickn. | Sisyrinchium nashii | Iridaceae
|
| SIFU | Sisyrinchium funereum Bickn. | Funeral Mountain blue-eyed grass | Iridaceae
|
| SIFU2 | Sisyrinchium fuscatum Bickn. | coastalplain blue-eyed grass | Iridaceae
|
| SIGR10 | Sisyrinchium graminoides Bickn. | Sisyrinchium angustifolium | Iridaceae
|
| SIGR7 | Sisyrinchium greenei Bickn. | Sisyrinchium bellum | Iridaceae
|