| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| HYREI | Hymenostylium recurvirostre (Hedw.) Dix. var. insigne (Dix.) Bartr. | Hymenostylium insigne | Pottiaceae
|
| HYREL | Hymenostylium recurvirostre (Hedw.) Dix. var. latifolium (Zett.) Wijk & Marg. | Hymenostylium recurvirostre | Pottiaceae
|
| HYRE71 | Hymenostylium recurvirostre (Hedw.) Dix. | hymenostylium moss | Pottiaceae
|
| HYSC7 | Hymenostylium scabrum (Lindb.) Loeske | Hymenostylium recurvirostre | Pottiaceae
|
| HYMEN11 | Hymenostylium Brid. | hymenostylium moss | Pottiaceae
|
| HYLO | Hymenothrix loomisii Blake | Loomis' thimblehead | Asteraceae
|
| HYWI | Hymenothrix wislizeni Gray | TransPecos thimblehead | Asteraceae
|
| HYWR | Hymenothrix wrightii Gray | Wright's thimblehead | Asteraceae
|
| HYMEN6 | Hymenothrix Gray | thimblehead | Asteraceae
|
| HYACA2 | Hymenoxys acaulis (Pursh) Parker var. arizonica (Greene) Parker | Tetraneuris acaulis var. arizonica | Asteraceae
|
| HYACC2 | Hymenoxys acaulis (Pursh) Parker var. caespitosa (A. Nels.) Parker | Tetraneuris acaulis var. caespitosa | Asteraceae
|
| HYACE | Hymenoxys acaulis (Pursh) Parker var. epunctata (A. Nels.) Cronq. | Tetraneuris acaulis var. epunctata | Asteraceae
|
| HYACG | Hymenoxys acaulis (Pursh) Parker var. glabra (Gray) Parker | Tetraneuris herbacea | Asteraceae
|
| HYACI3 | Hymenoxys acaulis (Pursh) Parker var. ivesiana (Greene) Parker | Tetraneuris ivesiana | Asteraceae
|
| HYACL | Hymenoxys acaulis (Pursh) Parker var. lanata (Greene) Cronq. | Tetraneuris acaulis var. caespitosa | Asteraceae
|
| HYACN | Hymenoxys acaulis (Pursh) Parker var. nana Welsh | Tetraneuris acaulis var. nana | Asteraceae
|
| HYAC4 | Hymenoxys acaulis (Pursh) Parker | Tetraneuris acaulis var. acaulis | Asteraceae
|
| HYAM8 | Hymenoxys ambigens (Blake) Bierner | Pinaleno Mountain rubberweed | Asteraceae
|
| HYAN | Hymenoxys anthemoides (Juss.) Cass. | South American rubberweed | Asteraceae
|
| HYARI | Hymenoxys argentea (Gray) Parker var. ivesiana (Greene) Cronq. | Tetraneuris ivesiana | Asteraceae
|
| HYAR5 | Hymenoxys argentea (Gray) Parker | Tetraneuris argentea | Asteraceae
|
| HYBI2 | Hymenoxys bigelovii (Gray) Parker | Bigelow's rubberweed | Asteraceae
|
| HYBR7 | Hymenoxys brachyactis Woot. & Standl. | East View rubberweed | Asteraceae
|
| HYBR | Hymenoxys brandegeei Porter ex Gray | Tetraneuris brandegeei | Asteraceae
|
| HYCOC | Hymenoxys cooperi (Gray) Cockerell var. canescens (D.C. Eat.) Parker | Cooper's rubberweed | Asteraceae
|
| HYCOC2 | Hymenoxys cooperi (Gray) Cockerell var. cooperi | Cooper's rubberweed | Asteraceae
|
| HYCO2 | Hymenoxys cooperi (Gray) Cockerell | Cooper's rubberweed | Asteraceae
|
| HYDE5 | Hymenoxys depressa (Torr. & Gray ex Gray) Welsh & Reveal | Tetraneuris depressa | Asteraceae
|
| HYGL5 | Hymenoxys glabra (Nutt.) Shinners | Tetraneuris scaposa var. scaposa | Asteraceae
|
| HYGR5 | Hymenoxys grandiflora (Torr. & Gray ex Gray) Parker | Tetraneuris grandiflora | Asteraceae
|
| HYHE | Hymenoxys helenioides (Rydb.) Cockerell | Intermountain rubberweed | Asteraceae
|
| HYHE4 | Hymenoxys herbacea (Greene) Cusick | Tetraneuris herbacea | Asteraceae
|
| HYHO | Hymenoxys hoopesii (Gray) Bierner | owl's-claws | Asteraceae
|
| HYIV | Hymenoxys ivesiana (Greene) Parker | Tetraneuris ivesiana | Asteraceae
|
| HYJA | Hymenoxys jamesii Bierner | Jame's rubberweed | Asteraceae
|
| HYLA7 | Hymenoxys ?lapidicola Welsh & Neese | stone rubberweed | Asteraceae
|
| HYLE | Hymenoxys lemmonii (Greene) Cockerell | Lemmon's rubberweed | Asteraceae
|
| HYLI7 | Hymenoxys linearifolia Hook. | Tetraneuris linearifolia var. linearifolia | Asteraceae
|
| HYMI10 | Hymenoxys microcephala (Gray) Bierner | Apache Passe rubberweed | Asteraceae
|
| HYOD | Hymenoxys odorata DC. | bitter rubberweed | Asteraceae
|
| HYOL | Hymenoxys olivacea Cockerell | Hymenoxys richardsonii var. floribunda | Asteraceae
|
| HYQU2 | Hymenoxys quinquesquamata Rydb. | rincon rubberweed | Asteraceae
|
| HYRIF | Hymenoxys richardsonii (Hook.) Cockerell var. floribunda (Gray) Parker | Colorado rubberweed | Asteraceae
|
| HYRIR | Hymenoxys richardsonii (Hook.) Cockerell var. richardsonii | pingue rubberweed | Asteraceae
|
| HYRIU | Hymenoxys richardsonii (Hook.) Cockerell var. utahensis Cockerell | Hymenoxys richardsonii var. floribunda | Asteraceae
|
| HYRI | Hymenoxys richardsonii (Hook.) Cockerell | pingue rubberweed | Asteraceae
|
| HYRU | Hymenoxys rusbyi (Gray) Cockerell | Rusby's rubberweed | Asteraceae
|
| HYSCA | Hymenoxys scaposa (DC.) Parker var. argyrocaulon Parker | Tetraneuris scaposa var. argyrocaulon | Asteraceae
|
| HYSCG | Hymenoxys scaposa (DC.) Parker var. glabra (Nutt.) Parker | Tetraneuris scaposa var. scaposa | Asteraceae
|
| HYSCL | Hymenoxys scaposa (DC.) Parker var. linearis (Nutt.) Parker | Tetraneuris scaposa var. linearis | Asteraceae
|
| HYSCV | Hymenoxys scaposa (DC.) Parker var. villosa Shinners | Tetraneuris scaposa var. villosa | Asteraceae
|
| HYSC3 | Hymenoxys scaposa (DC.) Parker | Tetraneuris scaposa var. scaposa | Asteraceae
|
| HYSU | Hymenoxys subintegra Cockerell | Arizona rubberweed | Asteraceae
|
| HYTE5 | Hymenoxys texana (Coult. & Rose) Cockerell | prairiedawn | Asteraceae
|
| HYTO2 | Hymenoxys torreyana (Nutt.) Parker | Tetraneuris torreyana | Asteraceae
|
| HYTU3 | Hymenoxys turneri Parker | Tetraneuris turneri | Asteraceae
|
| HYVA | Hymenoxys vaseyi (Gray) Cockerell | Vasey's rubberweed | Asteraceae
|
| HYMEN7 | Hymenoxys Cass. | rubberweed | Asteraceae
|
| HYIN5 | Hyophila involuta (Hook.) Jaeg. | hyophila moss | Pottiaceae
|
| HYRI3 | Hyophila riparia (Aust.) Fleisch. in Britt. | Hyophila involuta | Pottiaceae
|
| HYST6 | Hyophila stanfordensis (Steere) A. J. E. Sm. & H. Whiteh. | Tortula stanfordensis | Pottiaceae
|
| HYTO4 | Hyophila tortula (Schwaegr.) Hampe | Hyophila involuta | Pottiaceae
|
| HYOPH | Hyophila Brid. | hyophila moss | Pottiaceae
|
| HYSP8 | Hyophilopsis sprengelii (Schwaegr.) Crum | Neohyophila sprengelii | Pottiaceae
|
| HYAL2 | Hyoscyamus albus L. | white henbane | Solanaceae
|
| HYMU3 | Hyoscyamus muticus L. | henbane | Solanaceae
|
| HYNI | Hyoscyamus niger L. | black henbane | Solanaceae
|
| HYOSC | Hyoscyamus L. | henbane | Solanaceae
|
| HYBI5 | Hyoseris biflora Walt. | Krigia biflora var. biflora | Asteraceae
|
| HYMI6 | Hyoseris minima L. | Arnoseris minima | Asteraceae
|
| HYVI5 | Hyoseris virginica L. | Krigia virginica | Asteraceae
|
| HYDR4 | Hyparrhenia dregeana (Nees) Stent | silky thatching grass | Poaceae
|
| HYFI3 | Hyparrhenia filipendula (Hochst.) Stapf | hyparrhenia | Poaceae
|
| HYHI | Hyparrhenia hirta (L.) Stapf | thatching grass | Poaceae
|
| HYRU2 | Hyparrhenia rufa (Nees) Stapf | jaraguagrass | Poaceae
|
| HYPAR | Hyparrhenia Anderss. ex Fourn. | thatching grass | Poaceae
|
| HYGR4 | Hypecoum grandiflorum Benth. | Hypecoum imberbe | Fumariaceae
|
| HYIM | Hypecoum imberbe Sm. | sicklefruit hypecoum | Fumariaceae
|
| HYPE8 | Hypecoum pendulum L. | nodding hypecoum | Fumariaceae
|
| HYPEC | Hypecoum L. | hypecoum | Fumariaceae
|
| HYTR | Hypelate trifoliata Sw. | inkwood | Sapindaceae
|
| HYPEL | Hypelate P. Br. | hypelate | Sapindaceae
|
| HYDO2 | Hyperbaena domingensis (DC.) Benth. | forest snakevine | Menispermaceae
|
| HYLA8 | Hyperbaena laurifolia (Poir.) Urban | limestone snakevine | Menispermaceae
|
| HYPER2 | Hyperbaena Miers ex Benth. | hyperbaena | Menispermaceae
|
| HYAC2 | Hypericum acutifolium Ell. | sharpleaf St. Johnswort | Clusiaceae
|
| HYAD | Hypericum adpressum Raf. ex W. Bart. | creeping St. Johnswort | Clusiaceae
|
| HYAM6 | Hypericum ambiguum Ell. | Hypericum galioides | Clusiaceae
|
| HYAN2 | Hypericum anagalloides Cham. & Schlecht. | tinker's penny | Clusiaceae
|
| HYAN8 | Hypericum androsaemum L. | | Clusiaceae
|
| HYAP2 | Hypericum apocynifolium Small | Hypericum nudiflorum | Clusiaceae
|
| HYAS80 | Hypericum ascyron L. | great St. Johnswort | Clusiaceae
|
| HYAS3 | Hypericum aspalathoides Willd. p.p. | Hypericum brachyphyllum | Clusiaceae
|
| HYAS3 | Hypericum aspalathoides Willd. p.p. | Hypericum reductum | Clusiaceae
|
| HYAU | Hypericum aureum Bartr. | Hypericum frondosum | Clusiaceae
|
| HYBI4 | Hypericum bissellii B.L. Robins. | Hypericum dolabriforme | Clusiaceae
|
| HYBO2 | Hypericum boreale (Britt.) Bickn. | northern St. Johnswort | Clusiaceae
|
| HYBR3 | Hypericum brachyphyllum (Spach) Steud. | coastalplain St. Johnswort | Clusiaceae
|
| HYBU | Hypericum buckleii M.A. Curtis | Buckley's St. Johnswort | Clusiaceae
|
| HYCA10 | Hypericum calycinum L. | Aaron's beard | Clusiaceae
|
| HYCAG | Hypericum canadense L. var. galiiforme Fern. | Hypericum canadense | Clusiaceae
|