| Symbol | Scientific name | Common name/Accepted name (for synonyms) | Family |
| MAPOM | Marchantia polymorpha L. ssp. montivagans Bischl. & Boisselier | | Marchantiaceae
|
| MAPOP | Marchantia polymorpha L. ssp. polymorpha | | Marchantiaceae
|
| MAPOR | Marchantia polymorpha L. ssp. ruderalis Bischl. & Boisselier | | Marchantiaceae
|
| MAPO16 | Marchantia polymorpha L. | | Marchantiaceae
|
| MARCH | Marchantia L. | | Marchantiaceae
|
| MALE5 | Margaranthus lemmonii Gray | Margaranthus solanaceus | Solanaceae
|
| MAPU12 | Margaranthus purpurascens Rydb. | Margaranthus solanaceus | Solanaceae
|
| MASO4 | Margaranthus solanaceus Schlecht. | netted globecherry | Solanaceae
|
| MARGA | Margaranthus Schlecht. | margaranthus | Solanaceae
|
| MANO | Margaritaria nobilis L. f. | bastard hogberry | Euphorbiaceae
|
| MARGA2 | Margaritaria L. f. | margaritaria | Euphorbiaceae
|
| MAPO10 | Marginaria polypodioides (L.) Tidestrom | Pleopeltis polypodioides ssp. polypodioides | Polypodiaceae
|
| MAMA27 | Mariana mariana (L.) Hill | Silybum marianum | Asteraceae
|
| MAJA4 | Marilaunidium jamaicense (L.) Kuntze | Nama jamaicense | Hydrophyllaceae
|
| MACA8 | Marina calycosa (Gray) Barneby | San Pedro false prairie-clover | Fabaceae
|
| MADI4 | Marina diffusa (Moric.) Barneby | spreading false prairie-clover | Fabaceae
|
| MAOR4 | Marina orcuttii (S. Wats.) Barneby | Sonoran false prairie-clover | Fabaceae
|
| MAPA7 | Marina parryi (Torr. & Gray) Barneby | Parry's false prairie-clover | Fabaceae
|
| MARIN | Marina Liebm. | false prairie-clover | Fabaceae
|
| MASI6 | Mariposa simulans Hoover | Calochortus simulans | Liliaceae
|
| MACA12 | Mariscus californicus (S. Wats.) Britt. | Cladium californicum | Cyperaceae
|
| MACA13 | Mariscus capillaris (Sw.) Vahl | Cyperus nanus var. subtenuis | Cyperaceae
|
| MACA14 | Mariscus cayennensis (Lam.) Urban | Cyperus aggregatus | Cyperaceae
|
| MACO19 | Mariscus confertus (Sw.) C.B. Clarke | Cyperus confertus | Cyperaceae
|
| MACO18 | Mariscus congestus (Vahl) C.B. Clarke | Cyperus congestus | Cyperaceae
|
| MACY5 | Mariscus cylindricus Ell. | Cyperus retrorsus var. retrorsus | Cyperaceae
|
| MACY4 | Mariscus cyperinus (Retz.) Vahl | Cyperus cyperinus | Cyperaceae
|
| MAFA7 | Mariscus fauriei (K�kenth.) T. Koyama | Cyperus fauriei | Cyperaceae
|
| MAFE2 | Mariscus fendlerianus (Boeckl.) T. Koyama | Cyperus fendlerianus | Cyperaceae
|
| MAFI2 | Mariscus filiculmis auct. non (Vahl) T. Koyama | Cyperus lupulinus ssp. lupulinus | Cyperaceae
|
| MAFL6 | Mariscus flavus Vahl | Cyperus aggregatus | Cyperaceae
|
| MAFU3 | Mariscus fuligineus (Chapman) C.B. Clarke | Cyperus fuligineus | Cyperaceae
|
| MAGL8 | Mariscus globulosus auct. non (Aubl.) Urban | Cyperus croceus | Cyperaceae
|
| MAGR11 | Mariscus gracilis Vahl | Cyperus swartzii | Cyperaceae
|
| MAHID | Mariscus hillebrandii (Boeckl.) T. Koyama ssp. decipiens (Hbd.) T. Koyama | Cyperus hillebrandii var. decipiens | Cyperaceae
|
| MAHI3 | Mariscus hillebrandii (Boeckl.) T. Koyama | Cyperus hillebrandii var. hillebrandii | Cyperaceae
|
| MAHU | Mariscus huarmensis Kunth | Cyperus odoratus | Cyperaceae
|
| MAHYB | Mariscus hypochlorus (Hbd.) C.B. Clarke ssp. brevior (K�kenth.) T. Koyama | Cyperus hypochlorus var. brevior | Cyperaceae
|
| MAHY2 | Mariscus hypochlorus (Hbd.) C.B. Clarke | Cyperus hypochlorus var. hypochlorus | Cyperaceae
|
| MAJA3 | Mariscus jamaicensis (Crantz) Britt. | Cladium mariscus ssp. jamaicense | Cyperaceae
|
| MAJA5 | Mariscus javanicus (Houtt.) Merr. & Metcalfe | Cyperus javanicus | Cyperaceae
|
| MAKU | Mariscus kunthianus Gaud. | Cyperus kunthianus | Cyperaceae
|
| MALI5 | Mariscus ligularis (L.) Urban | Cyperus ligularis | Cyperaceae
|
| MAMA20 | Mariscus mariscoides (Muhl.) Kuntze | Cladium mariscoides | Cyperaceae
|
| MAME7 | Mariscus meyenianus (Kunth) Nees | Cyperus meyenianus | Cyperaceae
|
| MAMU4 | Mariscus mutisii Kunth | Cyperus mutisii | Cyperaceae
|
| MAPE6 | Mariscus pedunculatus (R. Br.) T. Koyama | Remirea maritima | Cyperaceae
|
| MAPEB | Mariscus pennatiformis (K�kenth.) T. Koyama ssp. bryanii (K�kenth.) T. Koyama | Cyperus pennatiformis var. bryanii | Cyperaceae
|
| MAPE5 | Mariscus pennatiformis (K�kenth.) T. Koyama | Cyperus pennatiformis var. pennatiformis | Cyperaceae
|
| MAPHH | Mariscus phleoides Nees ex Kunth ssp. hawaiensis (Mann) T. Koyama | Cyperus phleoides var. hawaiensis | Cyperaceae
|
| MAPH5 | Mariscus phleoides Nees ex Kunth | Cyperus phleoides var. phleoides | Cyperaceae
|
| MAPL4 | Mariscus planifolius (L.C. Rich.) Urban | Cyperus planifolius | Cyperaceae
|
| MAPO8 | Mariscus polystachyos auct. non A. Rich. | Cyperus polystachyos var. polystachyos | Cyperaceae
|
| MAPU13 | Mariscus pubescens J.& K. Presl, non Cyperus pubescens Steud. | Cyperus dentoniae | Cyperaceae
|
| MARE9 | Mariscus restioides (Sw.) Kuntze | Machaerina restioides | Cyperaceae
|
| MARO7 | Mariscus rockii (K�kenth.) T. Koyama | Cyperus rockii | Cyperaceae
|
| MASA6 | Mariscus sandwicensis (K�kenth.) T. Koyama | Cyperus sandwicensis | Cyperaceae
|
| MASC7 | Mariscus schweinitzii (Torr.) T. Koyama | Cyperus schweinitzii | Cyperaceae
|
| MAUR2 | Mariscus urbanii (Boeckl.) C.B. Clarke | Cyperus urbanii | Cyperaceae
|
| MAHI7 | Markhamia hildebrantii (Baker) Sprague | Markhamia lutea | Bignoniaceae
|
| MALU4 | Markhamia lutea (Benth.) K. Schum. | siala | Bignoniaceae
|
| MARKH | Markhamia Seem. Ex Baill. | markhamia | Bignoniaceae
|
| MASI3 | Marlierea sintenisii Kiaersk. | beruquillo | Myrtaceae
|
| MARLI | Marlierea Camb. | marlierea | Myrtaceae
|
| MACA18 | Maronea carolinae H. Magn. | | Fuscideaceae
|
| MACO28 | Maronea constans (Nyl.) Hepp | | Fuscideaceae
|
| MAPO11 | Maronea polyphaea H. Magn. | | Fuscideaceae
|
| MAPO12 | Maronea porinoidea Zahlbr. | Ramonia valenzueliana | Gyalectaceae
|
| MARON | Maronea A. Massal. | maronea | Fuscideaceae
|
| MAIN19 | Marrubium incanum Desr. | horehound | Lamiaceae
|
| MAVU | Marrubium vulgare L. | horehound | Lamiaceae
|
| MARRU | Marrubium L. | horehound | Lamiaceae
|
| MAEL4 | Marsdenia elliptica Dcne. | jungle netvine | Asclepiadaceae
|
| MARE12 | Marsdenia reichenbachii Triana | condorvine | Asclepiadaceae
|
| MARSD | Marsdenia R. Br. | marsdenia | Asclepiadaceae
|
| MACAC2 | Marshallia caespitosa Nutt. ex DC. var. caespitosa | puffballs | Asteraceae
|
| MACAS | Marshallia caespitosa Nutt. ex DC. var. signata Beadle & F.E. Boynt. | puffballs | Asteraceae
|
| MACA7 | Marshallia caespitosa Nutt. ex DC. | puffballs | Asteraceae
|
| MAGRT2 | Marshallia graminifolia (Walt.) Small ssp. tenuifolia (Raf.) L. Watson | Marshallia graminifolia var. cynanthera | Asteraceae
|
| MAGRC2 | Marshallia graminifolia (Walt.) Small var. cynanthera (Ell.) Beadle & F.E. Boynt. | grassleaf Barbara's buttons | Asteraceae
|
| MAGRG3 | Marshallia graminifolia (Walt.) Small var. graminifolia | grassleaf Barbara's buttons | Asteraceae
|
| MAGR6 | Marshallia graminifolia (Walt.) Small | grassleaf Barbara's buttons | Asteraceae
|
| MAGR7 | Marshallia grandiflora Beadle & F.E. Boynt. | Monongahela Barbara's buttons | Asteraceae
|
| MALA4 | Marshallia laciniarioides Small | Marshallia graminifolia var. graminifolia | Asteraceae
|
| MAMO3 | Marshallia mohrii Beadle & F.E. Boynt. | Mohr's Barbara's buttons | Asteraceae
|
| MAOBO | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. obovata | spoonshape Barbara's buttons | Asteraceae
|
| MAOBP | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. platyphylla (M.A. Curtis) Beadle & F.E. Boynt. | Marshallia obovata var. obovata | Asteraceae
|
| MAOBS | Marshallia obovata (Walt.) Beadle & F.E. Boynt. var. scaposa Channell | spoonshape Barbara's buttons | Asteraceae
|
| MAOB | Marshallia obovata (Walt.) Beadle & F.E. Boynt. | spoonshape Barbara's buttons | Asteraceae
|
| MARA6 | Marshallia ramosa Beadle & F.E. Boynt. | southern Barbara's buttons | Asteraceae
|
| MATEG | Marshallia tenuifolia Raf. var. graminifolia (Walt.) Gandhi & Thomas | Marshallia graminifolia var. graminifolia | Asteraceae
|
| MATE6 | Marshallia tenuifolia Raf. | Marshallia graminifolia var. cynanthera | Asteraceae
|
| MATR2 | Marshallia trinervia (Walt.) Trel. | broadleaf Barbara's buttons | Asteraceae
|
| MAWI4 | Marshallia williamsonii Small | Marshallia graminifolia var. graminifolia | Asteraceae
|
| MARSH | Marshallia Schreb. | Barbara's buttons | Asteraceae
|
| MAAN14 | Marsilea ancylopoda A. Braun | tropical waterclover | Marsileaceae
|
| MABE | Marsilea berteroi A. Braun | Marsilea ancylopoda | Marsileaceae
|
| MAFO4 | Marsilea fournieri C. Christens. | Marsilea vestita ssp. vestita | Marsileaceae
|
| MAHI6 | Marsilea hirsuta R. Br. | rough waterclover | Marsileaceae
|
| MAMA9 | Marsilea macropoda Engelm. ex A. Braun | bigfoot waterclover | Marsileaceae
|
| MAME3 | Marsilea mexicana A. Braun | Marsilea ancylopoda | Marsileaceae
|