| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| SIHA4 | Sisyrinchium hastile Bickn. p.p. | Sisyrinchium albidum | Iridaceae
|
| SIHE10 | Sisyrinchium helleri Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SIHE7 | Sisyrinchium hesperium Bickn. | Sisyrinchium bellum | Iridaceae
|
| SIHE11 | Sisyrinchium heterocarpum Bickn. | Sisyrinchium montanum var. montanum | Iridaceae
|
| SIHI4 | Sisyrinchium hitchcockii D. Henderson | Hitchcock's blue-eyed grass | Iridaceae
|
| SIIDI | Sisyrinchium idahoense Bickn. var. idahoense | Idaho blue-eyed grass | Iridaceae
|
| SIIDM | Sisyrinchium idahoense Bickn. var. macounii (Bickn.) D. Henderson | Macoun's blue-eyed grass | Iridaceae
|
| SIIDO | Sisyrinchium idahoense Bickn. var. occidentale (Bickn.) D. Henderson | Idaho blue-eyed grass | Iridaceae
|
| SIIDS | Sisyrinchium idahoense Bickn. var. segetum (Bickn.) D. Henderson | Idaho blue-eyed grass | Iridaceae
|
| SIID | Sisyrinchium idahoense Bickn. | Idaho blue-eyed grass | Iridaceae
|
| SIIM | Sisyrinchium implicatum Bickn. | blueeyed grass | Iridaceae
|
| SIIN14 | Sisyrinchium inalatum A. Nels. | Olsynium douglasii var. douglasii | Iridaceae
|
| SIIN16 | Sisyrinchium incrustatum Bickn. | Sisyrinchium fuscatum | Iridaceae
|
| SIIN15 | Sisyrinchium inflatum (Suksdorf) St. John | Olsynium douglasii var. inflatum | Iridaceae
|
| SIIN17 | Sisyrinchium intermedium Bickn. | Sisyrinchium mucronatum | Iridaceae
|
| SIIR2 | Sisyrinchium iridifolium Kunth | spreading blue-eyed grass | Iridaceae
|
| SIKA2 | Sisyrinchium kansanum (Bickn.) Alexander | Sisyrinchium campestre | Iridaceae
|
| SILA5 | Sisyrinchium langloisii Greene | roadside blue-eyed grass | Iridaceae
|
| SILA18 | Sisyrinchium laxum Otto ex Sims | Sisyrinchium iridifolium | Iridaceae
|
| SILI4 | Sisyrinchium littorale Greene | Alaska blue-eyed grass | Iridaceae
|
| SILO6 | Sisyrinchium longipedunculatum Bickn. | Sisyrinchium demissum | Iridaceae
|
| SILO5 | Sisyrinchium longipes (Bickn.) Kearney & Peebles | timberland blue-eyed grass | Iridaceae
|
| SIMA10 | Sisyrinchium macounii Bickn. | Sisyrinchium idahoense var. macounii | Iridaceae
|
| SIMA8 | Sisyrinchium macrocarpon Bickn. | Willow Spring blue-eyed grass | Iridaceae
|
| SIMI4 | Sisyrinchium miamiense Bickn. | Miami blue-eyed grass | Iridaceae
|
| SIMI | Sisyrinchium micranthum auct. non Cav. | Sisyrinchium rosulatum | Iridaceae
|
| SIMI2 | Sisyrinchium minus Engelm. & Gray | dwarf blue-eyed grass | Iridaceae
|
| SIMOC2 | Sisyrinchium montanum Greene ssp. crebrum (Fern.) B�cher | Sisyrinchium montanum var. crebrum | Iridaceae
|
| SIMOC | Sisyrinchium montanum Greene var. crebrum Fern. | strict blue-eyed grass | Iridaceae
|
| SIMOM | Sisyrinchium montanum Greene var. montanum | strict blue-eyed grass | Iridaceae
|
| SIMO2 | Sisyrinchium montanum Greene | strict blue-eyed grass | Iridaceae
|
| SIMUA | Sisyrinchium mucronatum Michx. var. atlanticum (Bickn.) Ahles | Sisyrinchium atlanticum | Iridaceae
|
| SIMU3 | Sisyrinchium mucronatum Michx. | needletip blue-eyed grass | Iridaceae
|
| SINA | Sisyrinchium nashii Bickn. | Nash's blue-eyed grass | Iridaceae
|
| SIOC2 | Sisyrinchium occidentale Bickn. | Sisyrinchium idahoense var. occidentale | Iridaceae
|
| SIPA11 | Sisyrinchium pallidum Cholewa & D. Henderson | pale blue-eyed grass | Iridaceae
|
| SIPO4 | Sisyrinchium powellii Warnock | Sisyrinchium cernuum | Iridaceae
|
| SIPR3 | Sisyrinchium pruinosum Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SIRA3 | Sisyrinchium radicatum Bickn. | bigroot blue-eyed grass | Iridaceae
|
| SIRO5 | Sisyrinchium rosulatum Bickn. | annual blue-eyed grass | Iridaceae
|
| SIRU4 | Sisyrinchium rufipes Bickn. | Sisyrinchium fuscatum | Iridaceae
|
| SISA3 | Sisyrinchium sagittiferum Bickn. | spearbract blue-eyed grass | Iridaceae
|
| SISA4 | Sisyrinchium sarmentosum Suksdorf ex Greene | mountain blue-eyed grass | Iridaceae
|
| SISC6 | Sisyrinchium scabrellum Bickn. | Sisyrinchium albidum | Iridaceae
|
| SISC3 | Sisyrinchium scabrum Cham. & Schlecht. | Sisyrinchium chilense | Iridaceae
|
| SISE7 | Sisyrinchium segetum Bickn. | Sisyrinchium idahoense var. segetum | Iridaceae
|
| SISE4 | Sisyrinchium septentrionale Bickn. | northern blue-eyed grass | Iridaceae
|
| SISO | Sisyrinchium solstitiale Bickn. | Sisyrinchium xerophyllum | Iridaceae
|
| SIST4 | Sisyrinchium strictum Bickn. | Sisyrinchium montanum var. montanum | Iridaceae
|
| SITO | Sisyrinchium tortum Bickn. | Sisyrinchium xerophyllum | Iridaceae
|
| SITR8 | Sisyrinchium tracyi Bickn. | blueeyed grass | Iridaceae
|
| SIVA2 | Sisyrinchium varians Bickn. | Sisyrinchium langloisii | Iridaceae
|
| SIXE | Sisyrinchium xerophyllum Greene | jeweled blue-eyed grass | Iridaceae
|
| SISYR | Sisyrinchium L. | blue-eyed grass | Iridaceae
|
| SIAN10 | Sitanion anomalum J.G. Sm. | Elymus hansenii | Poaceae
|
| SIEL6 | Sitanion elymoides Raf. | Elymus elymoides ssp. elymoides | Poaceae
|
| SIHA7 | Sitanion hansenii (Scribn.) J.G. Sm. | Elymus hansenii | Poaceae
|
| SIHO3 | Sitanion hordeoides Suksdorf | Elymus elymoides ssp. hordeoides | Poaceae
|
| SIHYB | Sitanion hystrix (Nutt.) J.G. Sm. var. brevifolium (J.G. Sm.) C.L. Hitchc. | Elymus elymoides ssp. brevifolius | Poaceae
|
| SIHYC | Sitanion hystrix (Nutt.) J.G. Sm. var. californicum (J.G. Sm.) F.D. Wilson | Elymus elymoides ssp. californicus | Poaceae
|
| SIHYH | Sitanion hystrix (Nutt.) J.G. Sm. var. hordeoides (Suksdorf) C.L. Hitchc. | Elymus elymoides ssp. hordeoides | Poaceae
|
| SIHY | Sitanion hystrix (Nutt.) J.G. Sm. | Elymus elymoides ssp. elymoides | Poaceae
|
| SIJU | Sitanion jubatum J.G. Sm. | Elymus multisetus | Poaceae
|
| SILO7 | Sitanion longifolium J.G. Sm. | Elymus elymoides ssp. brevifolius | Poaceae
|
| SIVE4 | Sitanion velutinum Piper | Elymus elymoides ssp. brevifolius | Poaceae
|
| SICA10 | Sitilias caroliniana (Walt.) Raf. | Pyrrhopappus carolinianus | Asteraceae
|
| SIMU5 | Sitilias multicaulis (DC.) Greene | Pyrrhopappus pauciflorus | Asteraceae
|
| SIAL9 | Sitodium altile Parkinson | Artocarpus altilis | Moraceae
|
| SICA12 | Sium carsonii Dur. ex Gray | Carson's waterparsnip | Apiaceae
|
| SICI2 | Sium cicutifolium Schrank | Sium suave | Apiaceae
|
| SIFL | Sium floridanum Small | Sium suave | Apiaceae
|
| SILA22 | Sium latifolium L. | wideleaf waterparsnip | Apiaceae
|
| SISI4 | Sium sisarum L. | skirret | Apiaceae
|
| SISUF | Sium suave Walt. var. floridanum (Small) C.F. Reed | Sium suave | Apiaceae
|
| SISU2 | Sium suave Walt. | hemlock waterparsnip | Apiaceae
|
| SIUM | Sium L. | waterparsnip | Apiaceae
|
| SKLA | Skottsbergiliana lasiocephala (Skottsberg) St. John | Sicyos lasiocephalus | Cucurbitaceae
|
| SKEL | Skyttea elachistophora (Nyl.) Sherwood & D. Hawksw. | | Odontotremataceae
|
| SKYTT2 | Skyttea Sherwood, D. Hawksw. & Coppins | skyttea | Odontotremataceae
|
| SKMU | Skyttella mulleri (Willey) D. Hawksw. & R. Sant. | | Uncertain Lichen Family
|
| SKYTT | Skyttella D. Hawksw. & R. Sant. | skyttella | Uncertain Lichen Family
|
| SLAM | Sloanea amygdalina Griseb. | motillo | Elaeocarpaceae
|
| SLBE | Sloanea berteriana Choisy ex DC. | bullwood | Elaeocarpaceae
|
| SLOAN | Sloanea L. | bullwood | Elaeocarpaceae
|
| SMUV | Smallanthus uvedalius (L.) Mackenzie ex Small | hairy leafcup | Asteraceae
|
| SMALL | Smallanthus Mackenzie ex Small | smallanthus | Asteraceae
|
| SMBOJ2 | Smelowskia borealis (Greene) Drury & Rollins ssp. jordalii (Drury & Rollins) Cody | Smelowskia borealis var. jordalii | Brassicaceae
|
| SMBOB | Smelowskia borealis (Greene) Drury & Rollins var. borealis | northern false candytuft | Brassicaceae
|
| SMBOJ | Smelowskia borealis (Greene) Drury & Rollins var. jordalii Drury & Rollins | Jordal's false candytuft | Brassicaceae
|
| SMBOK | Smelowskia borealis (Greene) Drury & Rollins var. koliana (Gomb�cz) Drury & Rollins | northern false candytuft | Brassicaceae
|
| SMBOV | Smelowskia borealis (Greene) Drury & Rollins var. villosa Drury & Rollins | villous false candytuft | Brassicaceae
|
| SMBO | Smelowskia borealis (Greene) Drury & Rollins | false candytuft | Brassicaceae
|
| SMCAI2 | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. ssp. integrifolia (Seem.) Hult�n | Smelowskia calycina var. integrifolia | Brassicaceae
|
| SMCAA | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. var. americana (Regel & Herder) Drury & Rollins | American false candytuft | Brassicaceae
|
| SMCAI | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. var. integrifolia (Seem.) Rollins | fernleaf false candytuft | Brassicaceae
|
| SMCAM | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. var. media Drury & Rollins | fernleaf false candytuft | Brassicaceae
|
| SMCAP | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. var. porsildii Drury & Rollins | Porsild's false candytuft | Brassicaceae
|
| SMCA | Smelowskia calycina (Steph. ex Willd.) C.A. Mey. | alpine smelowskia | Brassicaceae
|
| SMFRB | Smelowskia fremontii S. Wats. var. bisulcata (Greene) O.E. Schulz | Polyctenium fremontii var. bisulcatum | Brassicaceae
|
| SMFR | Smelowskia fremontii S. Wats. | Polyctenium fremontii var. fremontii | Brassicaceae
|
| SMHO | Smelowskia holmgrenii Rollins | Nye County false candytuft | Brassicaceae
|