| Common Name | Scientific Name | Code |
| n/a | Isoetes ?altonharvillii L.J. Musselman & R.D. Bray [engelmannii ? vallida] | ISAL4 |
| n/a | Isoetes ?brittonii Brunton & W.C. Taylor [engelmannii ? riparia] | ISBR5 |
| n/a | Isoetes ?bruntonii D.A. Knepper & L.J. Musselman [engelmannii ? hyemalis] | ISBR8 |
| n/a | Isoetes ?dodgei A.A. Eat. (pro sp.) [riparia ? tenella] | ISDO |
| n/a | Isoetes ?eatonii Dodge (pro sp.) [engelmannii ? tenella] | ISEA |
| n/a | Isoetes ?echtuckeri D.F. Brunton & D.M. Britton [tenella ? tuckermannii] | ISEC3 |
| n/a | Isoetes ?fairbrothersii J.D. Montgomery & W.C. Taylor [engelmannii ? lacustris] | ISFA |
| n/a | Isoetes ?foveolata A.A. Eat. ex Dodge (pro sp.) [engelmannii ? tuckermannii] | ISFO |
| n/a | Isoetes ?harveyi A.A. Eat. (pro sp.) [lacustris ? truncata] | ISHA4 |
| n/a | Isoetes ?heterospora A.A. Eat. (pro sp.) [lacustris ? tuckermannii] | ISHE |
| n/a | Isoetes ?hickeyi W.C. Taylor & N. Luebke [lacustris ? tenella] | ISHI2 |
| n/a | Isoetes ?pseudotruncata D.M. Britton & D.F. Brunton [echinospora ? maritima] | ISPS |
| n/a | Isoetes ?truncata (A.A. Eat.) Clute (pro sp.) [maritima ? tenella] | ISTR2 |
| n/a | Isoetes flaccida Shuttlw. ex A. Braun var. rigida Engelm. [excluded] | ISFLR2 |
| Acadian quillwort | Isoetes acadiensis Kott | ISAC |
| Ames's quillwort | Isoetes riparia Engelm. ex A. Braun var. amesii (A.A. Eat.) Proctor | ISRIA |
| Appalachian quillwort | Isoetes appalachiana D.F. Brunton & D.M. Britton | ISAP |
| Appalachian quillwort | Isoetes engelmannii A. Braun | ISEN |
| big-spore quillwort | Isoetes macrospora Durieu | ISMA |
| blackfoot quillwort | Isoetes melanopoda Gay & Durieu ex Durieu | ISME |
| blackspore quillwort | Isoetes melanospora Engelm. | ISME3 |
| Bolander's quillwort | Isoetes bolanderi Engelm. | ISBO |
| Boom's quillwort | Isoetes boomii N. Luebke | ISBO2 |
| Chapman's quillwort | Isoetes flaccida Shuttlw. ex A. Braun var. chapmanii Engelm. | ISFLC |
| evergreen quillwort | Isoetes hyemalis D.F. Brunton | ISHY |
| Georgia quillwort | Isoetes georgiana N. Luebke | ISGE |
| Hawai'i quillwort | Isoetes hawaiiensis W.C. Taylor & W.H. Wagner | ISHA5 |
| Howell's quillwort | Isoetes howellii Engelm. | ISHO |
| Isoetes ?eatonii | Isoetes eatonii Dodge var. gravesii (A.A. Eat.) Clute (pro syn.) | ISEAG |
| Isoetes ?eatonii | Isoetes gravesii A.A. Eat. | ISGR |
| Isoetes ?harveyi | Isoetes tuckermanii A. Braun var. harveyi (A.A. Eat.) Clute | ISTUH |
| Isoetes ?heterospora | Isoetes tuckermanii A. Braun var. heterospora (A.A. Eat.) Clute | ISTUH2 |
| Isoetes appalachiana | Isoetes engelmannii A. Braun var. georgiana Engelm. | ISENG |
| Isoetes bolanderi | Isoetes bolanderi Engelm. var. pygmaea (Engelm.) Clute | ISBOP |
| Isoetes bolanderi | Isoetes pygmaea Engelm. | ISPY2 |
| Isoetes engelmannii | Isoetes engelmannii A. Braun var. gracilis Engelm. | ISENG2 |
| Isoetes lacustris | Isoetes hieroglyphica A.A. Eat. | ISHI3 |
| Isoetes maritima | Isoetes echinospora Durieu ssp. maritima (Underwood) A. L?ve | ISECM4 |
| Isoetes maritima | Isoetes echinospora Durieu var. maritima (Underwood) A.A. Eat. | ISECM3 |
| Isoetes maritima | Isoetes muricata Durieu ssp. maritima (Underwood) Hult | ISMUM2 |
| Isoetes minima | Isoetes howellii Engelm. var. minima (A.A. Eat.) Pfeiffer | ISHOM |
| Isoetes occidentalis | Isoetes flettii (A.A. Eat.) N.E. Pfeiffer | ISFL2 |
| Isoetes occidentalis | Isoetes lacustris L. ssp. paupercula (Engelm.) J. Feilberg | ISLAP2 |
| Isoetes occidentalis | Isoetes lacustris L. var. paupercula Engelm. | ISLAP |
| Isoetes occidentalis | Isoetes paupercula (Engelm.) A.A. Eat. | ISPA2 |
| Isoetes occidentalis | Isoetes piperi A.A. Eat. | ISPI2 |
| Isoetes orcuttii | Isoetes nuttallii A. Braun ex Engelm. var. orcuttii (A.A. Eat.) Clute | ISNUO |
| Isoetes piedmontana | Isoetes virginica N.E. Pfeiffer var. piedmontana N.E. Pfeiffer | ISVIP |
| Isoetes riparia var. amesii | Isoetes riparia Engelm. ex A. Braun var. reticulata (A.A. Eat.) Proctor | ISRIR2 |
| Isoetes riparia var. amesii | Isoetes saccharata Engelm. var. amesii A.A. Eat. | ISSAA |
| Isoetes riparia var. riparia | Isoetes canadensis (Engelm.) A.A. Eat. | ISCA |
| Isoetes riparia var. riparia | Isoetes riparia Engelm. ex A. Braun var. canadensis Engelm. | ISRIC |
| Isoetes riparia var. riparia | Isoetes riparia Engelm. ex A. Braun var. palmeri (A.A. Eat.) Proctor | ISRIP |
| Isoetes riparia var. riparia | Isoetes riparia Engelm. ex A. Braun var. robbinsii (A.A. Eat.) Proctor | ISRIR3 |
| Isoetes saccharata | Calamaria saccharata (Engelm.) Kuntze | CASA17 |
| Isoetes tenella | Isoetes braunii Durieu | ISBR4 |
| Isoetes tenella | Isoetes echinospora Durieu | ISEC |
| Isoetes tenella | Isoetes echinospora Durieu ssp. asiatica (Makino) A. L?ve | ISECA |
| Isoetes tenella | Isoetes echinospora Durieu ssp. muricata (Durieu) A. & D. L?ve | ISECM |
| Isoetes tenella | Isoetes echinospora Durieu var. asiatica Makino | ISECA2 |
| Isoetes tenella | Isoetes echinospora Durieu var. braunii (Durieu) Engelm. | ISECB |
| Isoetes tenella | Isoetes echinospora Durieu var. hesperia (C.F. Reed) A. L?ve | ISECH |
| Isoetes tenella | Isoetes echinospora Durieu var. muricata (Durieu) Engelm. | ISECM2 |
| Isoetes tenella | Isoetes echinospora Durieu var. robusta Engelm. | ISECR |
| Isoetes tenella | Isoetes echinospora Durieu var. savilei Boivin | ISECS |
| Isoetes tenella | Isoetes muricata Durieu | ISMU2 |
| Isoetes tenella | Isoetes muricata Durieu var. braunii (Durieu) C.F. Reed | ISMUB |
| Isoetes tenella | Isoetes muricata Durieu var. hesperia C.F. Reed | ISMUH2 |
| Isoetes tenella | Isoetes setacea Lam. p.p. | ISSE4 |
| Isoetes tenella | Isoetes setacea Lam. ssp. muricata (Durieu) Holub | ISSEM |
| Isoetes valida | Isoetes caroliniana (A.A. Eat.) N. Luebke | ISCA4 |
| Isoetes valida | Isoetes engelmannii A. Braun var. caroliniana A.A. Eat. | ISENC |
| Isoetes valida | Isoetes engelmannii A. Braun var. valida Engelm. | ISENV |
| lake quillwort | Isoetes lacustris L. | ISLA |
| limestone quillwort | Isoetes butleri Engelm. | ISBU |
| Louisiana quillwort | Isoetes louisianensis Thieret | ISLO |
| maritime quillwort | Isoetes maritima Underwood | ISMA3 |
| Mattaponi quillwort | Isoetes mattaponica L.J. Musselman | ISMA7 |
| Merlin's grass | Isoetes tegetiformans Rury | ISTE |
| midget quillwort | Isoetes minima A.A. Eat. | ISMI4 |
| Nuttall's quillwort | Isoetes nuttallii A. Braun ex Engelm. | ISNU |
| Orcutt's quillwort | Isoetes orcuttii A.A. Eat. | ISOR |
| Peidmont quillwort | Isoetes piedmontana (N.E. Pfeiffer) C.F. Reed | ISPI |
| quillwort | Isoetes L. | ISOET |
| rock quillwort | Isoetes lithophila N.E. Pfeiffer | ISLI |
| rush quillwort | Isoetes junciformis D.F. Brunton & D.M. Britton | ISJU2 |
| shore quillwort | Isoetes riparia Engelm. ex A. Braun | ISRI |
| shore quillwort | Isoetes riparia Engelm. ex A. Braun var. riparia | ISRIR |
| southern quillwort | Isoetes flaccida Shuttlw. ex A. Braun | ISFL |
| southern quillwort | Isoetes flaccida Shuttlw. ex A. Braun var. alata N.E. Pfeiffer | ISFLA |
| southern quillwort | Isoetes flaccida Shuttlw. ex A. Braun var. flaccida | ISFLF |
| spike quillwort | Isoetes prototypus D.M. Britt. | ISPR |
| spiny-spore quillwort | Isoetes tenella L?man | ISTE5 |
| strong quillwort | Isoetes valida (Engelm.) Clute | ISVA2 |
| sugar quillwort | Isoetes saccharata Engelm. | ISSA |
| thin-wall quillwort | Isoetes microvela D.F. Brunton | ISMI3 |
| Tuckerman's quillwort | Isoetes tuckermanii A. Braun | ISTU |
| Virginia quillwort | Isoetes virginica N.E. Pfeiffer | ISVI |
| western quillwort | Isoetes occidentalis Henderson | ISOC |