| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| ISCU2 | Isopterygium cuspidifolium Card. | Taxiphyllum cuspidifolium | Hypnaceae
|
| ISDI5 | Isopterygium distichaceum (Mitt.) Jaeg. | Pseudotaxiphyllum distichaceum | Hypnaceae
|
| ISDR2 | Isopterygium drummondii Crum et al. | Isopterygium tenerum | Hypnaceae
|
| ISELG | Isopterygium elegans (Brid.) Lindb. var. gracilens Aust. ex Grout | Pseudotaxiphyllum elegans | Hypnaceae
|
| ISELS | Isopterygium elegans (Brid.) Lindb. var. schimperi (Jur. & Milde) Limpr. | Pseudotaxiphyllum elegans | Hypnaceae
|
| ISELT | Isopterygium elegans (Brid.) Lindb. var. terrestre (Lindb.) Wijk. & Marg. | Pseudotaxiphyllum elegans | Hypnaceae
|
| ISEL | Isopterygium elegans (Brid.) Lindb. | Pseudotaxiphyllum elegans | Hypnaceae
|
| ISFU2 | Isopterygium fulvum (Jaeg.) Kindb. | Isopterygium tenerum | Hypnaceae
|
| ISHO4 | Isopterygium homomallifolium Redf. | Pseudotaxiphyllum homomallifolium | Hypnaceae
|
| ISLA4 | Isopterygium latebricola (Schimp. in B.S.G.) Delogne | Plagiothecium latebricola | Plagiotheciaceae
|
| ISMIG | Isopterygium micans (Sw.) Kindb. var. groutii (Card. & Th�r.) Grout | Isopterygium tenerum | Hypnaceae
|
| ISMIL | Isopterygium micans (Sw.) Kindb. var. latifolium (Grout) Schornh. | Isopterygium tenerum | Hypnaceae
|
| ISMIM | Isopterygium micans (Sw.) Kindb. var. minus (Grout) Crum & Anderson | Isopterygium tenerum | Hypnaceae
|
| ISMI | Isopterygium micans (Sw.) Kindb. | Isopterygium tenerum | Hypnaceae
|
| ISMU4 | Isopterygium muellerianum (Schimp.) Jaeg. | Isopterygiopsis muelleriana | Hypnaceae
|
| ISNI | Isopterygium nitidulum (Wahlenb.) Kindb. | Isopterygiopsis pulchella | Hypnaceae
|
| ISNI2 | Isopterygium nitidum Lindb. | Isopterygiopsis pulchella | Hypnaceae
|
| ISPI3 | Isopterygium piliferum (Sw. ex Hartm.) Loeske | Plagiothecium piliferum | Plagiotheciaceae
|
| ISPUN | Isopterygium pulchellum (Hedw.) Jaeg. var. nitidulum (Wahlenb.) G. Roth | Isopterygiopsis pulchella | Hypnaceae
|
| ISPU71 | Isopterygium pulchellum (Hedw.) Jaeg. | Isopterygiopsis pulchella | Hypnaceae
|
| ISSE5 | Isopterygium seligeri (Brid.) Dix. in C. Jens. | Herzogiella seligeri | Hypnaceae
|
| ISSI | Isopterygium silesiacum (Selig. ex P. Beauv.) Kindb. | Herzogiella seligeri | Hypnaceae
|
| ISST3 | Isopterygium striatellum (Brid.) Loeske | Herzogiella striatella | Hypnaceae
|
| ISSU2 | Isopterygium subfalcatum (Aust.) Jaeg. | Pseudotaxiphyllum distichaceum | Hypnaceae
|
| ISTE3 | Isopterygium tenerum (Sw.) Mitt. | isopterygium moss | Hypnaceae
|
| ISTU2 | Isopterygium turfaceum (Lindb.) Lindb. | Herzogiella turfacea | Hypnaceae
|
| ISOPT3 | Isopterygium Mitt. | isopterygium moss | Hypnaceae
|
| ISBI2 | Isopyrum biternatum (Raf.) Torr. & Gray | Enemion biternatum | Ranunculaceae
|
| ISHA3 | Isopyrum hallii Gray | Enemion hallii | Ranunculaceae
|
| ISOC3 | Isopyrum occidentale Hook. & Arn. | Enemion occidentale | Ranunculaceae
|
| ISST2 | Isopyrum stipitatum Gray | Enemion stipitatum | Ranunculaceae
|
| ISAL2 | Isothecium alopecuroides (Dubois) Isov. | isothecium moss | Brachytheciaceae
|
| ISBR6 | Isothecium brachycladon Kindb. | Isothecium myosuroides | Brachytheciaceae
|
| ISBR7 | Isothecium brewerianum (Lesq.) Kindb. in Mac. & Kindb. | Isothecium cristatum | Brachytheciaceae
|
| ISCA3 | Isothecium cardotii Kindb. | Isothecium myosuroides | Brachytheciaceae
|
| ISCRH | Isothecium cristatum (Hampe) Robins. var. howei (Kindb.) Crum et al. | Isothecium cristatum | Brachytheciaceae
|
| ISCRL | Isothecium cristatum (Hampe) Robins. var. lutescens (Lesq. & James) Crum et al. | Isothecium cristatum | Brachytheciaceae
|
| ISCR | Isothecium cristatum (Hampe) Robins. | isothecium moss | Brachytheciaceae
|
| ISEUC | Isothecium eumyosuroides Dix. var. cavernarum (Mol.) Crum et al. | Isothecium myosuroides | Brachytheciaceae
|
| ISEU | Isothecium eumyosuroides Dix. | Isothecium myosuroides | Brachytheciaceae
|
| ISMYC | Isothecium myosuroides Brid. var. cavernarum Mol. | Isothecium myosuroides | Brachytheciaceae
|
| ISMY2 | Isothecium myosuroides Brid. | isothecium moss | Brachytheciaceae
|
| ISOB | Isothecium obtusatulum Kindb. | isothecium moss | Brachytheciaceae
|
| ISSPC | Isothecium spiculiferum (Mitt.) Ren. & Card. var. cardotii (Kindb. in Mac. & Kindb.) Crum et al. | Isothecium myosuroides | Brachytheciaceae
|
| ISSPM | Isothecium spiculiferum (Mitt.) Ren. & Card. var. myurellum (Kindb.) Wijk & Marg. | Isothecium myosuroides | Brachytheciaceae
|
| ISSP2 | Isothecium spiculiferum (Mitt.) Ren. & Card. | Isothecium myosuroides | Brachytheciaceae
|
| ISSTC | Isothecium stoloniferum Brid. var. cardotii (Kindb. in Mac. & Kindb.) Wijk & Marg. | Isothecium myosuroides | Brachytheciaceae
|
| ISSTM | Isothecium stoloniferum Brid. var. myurellum (Kindb.) Wijk & Marg. | Isothecium myosuroides | Brachytheciaceae
|
| ISSTS | Isothecium stoloniferum Brid. var. spiculiferum (Mitt.) R. D. Williams & Schof. | Isothecium myosuroides | Brachytheciaceae
|
| ISSTT | Isothecium stoloniferum Brid. var. thamnoides (Kindb.) Wijk & Marg. | Isothecium myosuroides | Brachytheciaceae
|
| ISST4 | Isothecium stoloniferum Brid. | Isothecium myosuroides | Brachytheciaceae
|
| ISTH | Isothecium thamnoides Kindb. | Isothecium myosuroides | Brachytheciaceae
|
| ISOTH | Isothecium Brid. | isothecium moss | Brachytheciaceae
|
| ISLO3 | Isotoma longiflora (L.) K. Presl | Hippobroma longiflora | Campanulaceae
|
| ISCA2 | Isotrema californica (Torr.) Huber | Aristolochia californica | Aristolochiaceae
|
| ISMA4 | Isotrema macrophyllum (Lam.) C.F. Reed | Aristolochia macrophylla | Aristolochiaceae
|
| ISTO | Isotrema tomentosa (Sims) Huber | Aristolochia tomentosa | Aristolochiaceae
|
| ISME2 | Isotria medeoloides (Pursh) Raf. | green fiveleaf orchid | Orchidaceae
|
| ISVE | Isotria verticillata Raf. | purple fiveleaf orchid | Orchidaceae
|
| ISOTR | Isotria Raf. | fiveleaf orchid | Orchidaceae
|
| ITVI | Itea virginica L. | Virginia sweetspire | Grossulariaceae
|
| ITEA | Itea L. | sweetspire | Grossulariaceae
|
| IVAC | Iva acerosa (Nutt.) R.C. Jackson | copperweed | Asteraceae
|
| IVAM | Iva ambrosiifolia (Gray) Gray | ragged marshelder | Asteraceae
|
| IVANL | Iva angustifolia Nutt. ex DC. var. latior Shinners | Iva texensis | Asteraceae
|
| IVAN | Iva angustifolia Nutt. ex DC. | narrowleaf marshelder | Asteraceae
|
| IVANA | Iva annua L. var. annua | annual marshelder | Asteraceae
|
| IVANC | Iva annua L. var. caudata (Small) R.C. Jackson | annual marshelder | Asteraceae
|
| IVANM | Iva annua L. var. ?macrocarpa (Blake) R.C. Jackson | annual marshelder | Asteraceae
|
| IVAN2 | Iva annua L. | annual marshelder | Asteraceae
|
| IVAS | Iva asperifolia Less. | Pensacola marshelder | Asteraceae
|
| IVAXR | Iva axillaris Pursh ssp. robustior (Hook.) Bassett | Iva axillaris | Asteraceae
|
| IVAXR2 | Iva axillaris Pursh var. robustior Hook. | Iva axillaris | Asteraceae
|
| IVAX | Iva axillaris Pursh | povertyweed | Asteraceae
|
| IVCA3 | Iva caudata Small | Iva annua var. caudata | Asteraceae
|
| IVCH | Iva cheiranthifolia Kunth | fly marshelder | Asteraceae
|
| IVCIM | Iva ciliata Willd. var. macrocarpa Blake | Iva annua var. macrocarpa | Asteraceae
|
| IVCI2 | Iva ciliata Willd. | Iva annua var. annua | Asteraceae
|
| IVDE | Iva dealbata Gray | woolly marshelder | Asteraceae
|
| IVFRF | Iva frutescens L. ssp. frutescens | Jesuit's bark | Asteraceae
|
| IVFRO2 | Iva frutescens L. ssp. oraria (Bartlett) R.C. Jackson | Jesuit's bark | Asteraceae
|
| IVFRO | Iva frutescens L. var. oraria (Bartlett) Fern. & Grisc. | Iva frutescens ssp. oraria | Asteraceae
|
| IVFR | Iva frutescens L. | Jesuit's bark | Asteraceae
|
| IVHA | Iva hayesiana Gray | San Diego povertyweed | Asteraceae
|
| IVIM | Iva imbricata Walt. | seacoast marshelder | Asteraceae
|
| IVMI | Iva microcephala Nutt. | piedmont marshelder | Asteraceae
|
| IVNE | Iva nevadensis M.E. Jones | Nevada sumpweed | Asteraceae
|
| IVTE | Iva texensis R.C. Jackson | Texas marshelder | Asteraceae
|
| IVXA | Iva xanthifolia Nutt. | giant sumpweed | Asteraceae
|
| IVA | Iva L. | marshelder | Asteraceae
|
| IVAPA | Ivesia aperta (J.T. Howell) Munz var. aperta | Sierra Valley mousetail | Rosaceae
|
| IVAPC | Ivesia aperta (J.T. Howell) Munz var. canina Ertter | Sierra Valley mousetail | Rosaceae
|
| IVAP | Ivesia aperta (J.T. Howell) Munz | Sierra Valley mousetail | Rosaceae
|
| IVAR | Ivesia argyrocoma (Rydb.) Rydb. | silverhair mousetail | Rosaceae
|
| IVARA | Ivesia arizonica (Eastw. ex J.T. Howell) Ertter var. arizonica | Arizona whitefeather | Rosaceae
|
| IVARS | Ivesia arizonica (Eastw. ex J.T. Howell) Ertter var. saxosa (Brandeg.) Ertter | rock whitefeather | Rosaceae
|
| IVAR2 | Ivesia arizonica (Eastw. ex J.T. Howell) Ertter | rock whitefeather | Rosaceae
|
| IVBAS2 | Ivesia baileyi S. Wats. ssp. setosa (S. Wats.) Keck | Ivesia baileyi var. setosa | Rosaceae
|
| IVBAT | Ivesia baileyi S. Wats. ssp. typica Keck | Ivesia baileyi var. baileyi | Rosaceae
|
| IVBAB | Ivesia baileyi S. Wats. var. baileyi | Bailey's ivesia | Rosaceae
|
| IVBAB2 | Ivesia baileyi S. Wats. var. beneolens (A. Nels. & J.F. Macbr.) Ertter | Bailey's ivesia | Rosaceae
|