| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| SUVI | Suksdorfia violacea Gray | violet suksdorfia | Saxifragaceae
|
| SUKSD | Suksdorfia Gray | suksdorfia | Saxifragaceae
|
| SUBA | Sulcaria badia Brodo & D. Hawksw. | | Alectoriaceae
|
| SUIS | Sulcaria isidiifera Brodo | | Alectoriaceae
|
| SULCA | Sulcaria Bystrek | sulcaria | Alectoriaceae
|
| SUHAH | Sullivantia hapemanii (Coult. & Fisher) Coult. var. hapemanii | Hapeman's coolwort | Saxifragaceae
|
| SUHAP | Sullivantia hapemanii (Coult. & Fisher) Coult. var. purpusii (Brand) Soltis | Purpus' sullivantia | Saxifragaceae
|
| SUHA | Sullivantia hapemanii (Coult. & Fisher) Coult. | Hapeman's coolwort | Saxifragaceae
|
| SUOH | Sullivantia ohionis Torr. & Gray ex Gray | Sullivantia sullivantii | Saxifragaceae
|
| SUOR | Sullivantia oregana S. Wats. | Oregon coolwort | Saxifragaceae
|
| SUPU | Sullivantia purpusii (Brand) Rosendahl | Sullivantia hapemanii var. purpusii | Saxifragaceae
|
| SURE | Sullivantia renifolia Rosendahl | Sullivantia sullivantii | Saxifragaceae
|
| SUSU3 | Sullivantia sullivantii (Torr. & Gray) Britt. | Sullivant's coolwort | Saxifragaceae
|
| SULLI | Sullivantia Torr. & Gray ex Gray | coolwort | Saxifragaceae
|
| SUMA2 | Suriana maritima L. | bay cedar | Surianaceae
|
| SURIA | Suriana L. | suriana | Surianaceae
|
| SUFR3 | Sutherlandia frutescens (L.) R. Br. | cancer bush | Fabaceae
|
| SUTHE | Sutherlandia R. Br. | sutherlandia | Fabaceae
|
| SWSA2 | Swainsona salsula (Pallas) Taubert | Sphaerophysa salsula | Fabaceae
|
| SWAL | Swallenia alexandrae (Swallen) S�derstrom & Decker | Eureka dunegrass | Poaceae
|
| SWALL | Swallenia S�derstrom & Decker | dunegrass | Poaceae
|
| SWGR | Swartzia grandiflora (Sw.) J.F. Gmel. | Solandra grandiflora | Solanaceae
|
| SWALC | Swertia albicaulis (Dougl. ex Griseb.) Kuntze var. columbiana (St. John) J. Pringle | Frasera albicaulis var. columbiana | Gentianaceae
|
| SWALC2 | Swertia albicaulis (Dougl. ex Griseb.) Kuntze var. cusickii (Gray) J. Pringle | Frasera albicaulis var. cusickii | Gentianaceae
|
| SWALI | Swertia albicaulis (Dougl. ex Griseb.) Kuntze var. idahoensis (St. John) J. Pringle | Frasera albicaulis var. idahoensis | Gentianaceae
|
| SWALN | Swertia albicaulis (Dougl. ex Griseb.) Kuntze var. nitida (Benth.) Jepson | Frasera albicaulis var. nitida | Gentianaceae
|
| SWAL2 | Swertia albicaulis (Dougl. ex Griseb.) Kuntze | Frasera albicaulis var. albicaulis | Gentianaceae
|
| SWALP | Swertia albomarginata (S. Wats.) Kuntze ssp. purpusii (Jepson) E. Murr. | Frasera puberulenta | Gentianaceae
|
| SWAL3 | Swertia albomarginata (S. Wats.) Kuntze | Frasera albomarginata | Gentianaceae
|
| SWBE | Swertia bethelii St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWCA2 | Swertia californica St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWCA | Swertia caroliniensis (Walt.) Kuntze | Frasera caroliniensis | Gentianaceae
|
| SWCO | Swertia coloradensis Rogers | Frasera coloradensis | Gentianaceae
|
| SWCO2 | Swertia columbiana St. John | Frasera albicaulis var. columbiana | Gentianaceae
|
| SWCU | Swertia cusickii (Gray) St. John | Frasera albicaulis var. cusickii | Gentianaceae
|
| SWEA | Swertia eastwoodiae St. John | Frasera albicaulis var. nitida | Gentianaceae
|
| SWFA | Swertia fastigiata Pursh | Frasera fastigiata | Gentianaceae
|
| SWGY | Swertia gypsicola Barneby | Frasera gypsicola | Gentianaceae
|
| SWID | Swertia idahoensis St. John | Frasera albicaulis var. idahoensis | Gentianaceae
|
| SWLA | Swertia lassenica St. John | Frasera albicaulis var. nitida | Gentianaceae
|
| SWMOA | Swertia modocensis St. John var. adglabra St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWMO2 | Swertia modocensis St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWMO | Swertia montana (Mulford) St. John | Frasera montana | Gentianaceae
|
| SWNE | Swertia neglecta (Hall) Jepson | Frasera neglecta | Gentianaceae
|
| SWNIC | Swertia nitida (Benth.) Jepson ssp. cusickii (Gray) Abrams | Frasera albicaulis var. cusickii | Gentianaceae
|
| SWNI | Swertia nitida (Benth.) Jepson | Frasera albicaulis var. nitida | Gentianaceae
|
| SWPA | Swertia pahutensis (Reveal) J. Pringle | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWPA2 | Swertia parryi (Torr.) Kuntze | Frasera parryi | Gentianaceae
|
| SWPEO | Swertia perennis L. var. obtusa (Ledeb.) Ledeb. ex Griseb. | Swertia perennis | Gentianaceae
|
| SWPE | Swertia perennis L. | felwort | Gentianaceae
|
| SWPU | Swertia puberulenta (A. Davids.) Jepson | Frasera puberulenta | Gentianaceae
|
| SWRAM | Swertia radiata (Kellogg) Kuntze var. macrophylla (Greene) St. John | Frasera speciosa | Gentianaceae
|
| SWRA | Swertia radiata (Kellogg) Kuntze | Frasera speciosa | Gentianaceae
|
| SWRE | Swertia recurva Sm. | Halenia recurva | Gentianaceae
|
| SWSH | Swertia shastensis St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWSI | Swertia sierrae St. John | Frasera albicaulis var. modocensis | Gentianaceae
|
| SWTU | Swertia tubulosa (Coville) Jepson | Frasera tubulosa | Gentianaceae
|
| SWUM | Swertia umpquaensis (M.E. Peck & Applegate) St. John | Frasera fastigiata | Gentianaceae
|
| SWUS | Swertia usambarensis Engl. | | Gentianaceae
|
| SWUT | Swertia utahensis (M.E. Jones) St. John | Frasera paniculata | Gentianaceae
|
| SWWA | Swertia watsonii St. John | Frasera albicaulis var. albicaulis | Gentianaceae
|
| SWERT | Swertia L. | felwort | Gentianaceae
|
| SWAL4 | Swida alternifolia (L. f.) Small | Cornus alternifolia | Cornaceae
|
| SWAM | Swida amomum (P. Mill.) Small | Cornus amomum | Cornaceae
|
| SWAS | Swida asperifolia (Michx.) Small | Cornus asperifolia | Cornaceae
|
| SWFO | Swida foemina (P. Mill.) Rydb. | Cornus foemina | Cornaceae
|
| SWIN | Swida instolonea (A. Nels.) Rydb. | Cornus sericea ssp. sericea | Cornaceae
|
| SWMI | Swida microcarpa (Nash) Small | Cornus asperifolia | Cornaceae
|
| SWPR | Swida priceae (Small) Small | Cornus drummondii | Cornaceae
|
| SWSA3 | Swida sanguinea (L.) Opiz | Cornus sanguinea | Cornaceae
|
| SWSE | Swida sericea (L.) Holub | Cornus sericea ssp. sericea | Cornaceae
|
| SWST2 | Swida stolonifera (Michx.) Rydb. | Cornus sericea ssp. sericea | Cornaceae
|
| SWST | Swida stricta (Lam.) Small | Cornus foemina | Cornaceae
|
| SWSU | Swida suecica (L.) Holub | Cornus suecica | Cornaceae
|
| SWMA | Swietenia macrophylla King | Honduras mahogany | Meliaceae
|
| SWMA2 | Swietenia mahagoni (L.) Jacq. | West Indian mahogany | Meliaceae
|
| SWIET | Swietenia Jacq. | mahogany | Meliaceae
|
| SYCO | Syagrus coronata (C. Martius) Becc. | Ouricury palm | Arecaceae
|
| SYRO2 | Syagrus romanzoffianum (Cham.) Glassman | Arecastrum romanzoffianum | Arecaceae
|
| SYAGR | Syagrus C. Martius | syagrus | Arecaceae
|
| SYHE4 | Symblepharis helicophylla Mont. | Symblepharis vaginata | Dicranaceae
|
| SYRA4 | Symblepharis raui (Aust.) Williams | Oncophorus raui | Dicranaceae
|
| SYVA2 | Symblepharis vaginata (Hook.) Wijk & Marg. | symblepharis moss | Dicranaceae
|
| SYMBL | Symblepharis Mont. | symblepharis moss | Dicranaceae
|
| SYRU3 | Sympetaleia rupestris (Baill.) Gray ex S. Wats. | Eucnide rupestris | Loasaceae
|
| SYAC | Symphoricarpos acutus (Gray) Dieck | sharpleaf snowberry | Caprifoliaceae
|
| SYALL2 | Symphoricarpos albus (L.) Blake ssp. laevigatus (Fern.) Hult�n | Symphoricarpos albus var. laevigatus | Caprifoliaceae
|
| SYALA | Symphoricarpos albus (L.) Blake var. albus | common snowberry | Caprifoliaceae
|
| SYALL | Symphoricarpos albus (L.) Blake var. laevigatus (Fern.) Blake | common snowberry | Caprifoliaceae
|
| SYALM | Symphoricarpos albus (L.) Blake var. mollis (Nutt.) Keck | Symphoricarpos mollis | Caprifoliaceae
|
| SYALP | Symphoricarpos albus (L.) Blake var. pauciflorus (W.J. Robins. ex Gray) Blake | Symphoricarpos albus var. albus | Caprifoliaceae
|
| SYAL | Symphoricarpos albus (L.) Blake | common snowberry | Caprifoliaceae
|
| SYGU | Symphoricarpos guadalupensis Correll | McKittrick's snowberry | Caprifoliaceae
|
| SYHE | Symphoricarpos hesperius G.N. Jones | trailing snowberry | Caprifoliaceae
|
| SYLO | Symphoricarpos longiflorus Gray | desert snowberry | Caprifoliaceae
|
| SYMI2 | Symphoricarpos microphyllus Kunth | pink snowberry | Caprifoliaceae
|
| SYMOH2 | Symphoricarpos mollis Nutt. ssp. hesperius (G.N. Jones) Abrams ex Ferris | Symphoricarpos hesperius | Caprifoliaceae
|
| SYMOA2 | Symphoricarpos mollis Nutt. var. acutus Gray | Symphoricarpos acutus | Caprifoliaceae
|
| SYMOH | Symphoricarpos mollis Nutt. var. hesperius (G.N. Jones) Cronq. | Symphoricarpos hesperius | Caprifoliaceae
|
| SYMO | Symphoricarpos mollis Nutt. | creeping snowberry | Caprifoliaceae
|
| SYOC | Symphoricarpos occidentalis Hook. | western snowberry | Caprifoliaceae
|