Key to Liverworts of Illinois (WIP)
Based on: Key to the Liverwort Genera in North America North of Mexico by Dale H. Vitt: https://bioone.org/journals/evansia/volume-40/issue-4/0747-9859-40.4.118/Key-to-the-Liverwort-Genera-in-North-America-North-of/10.1639/0747-9859-40.4.118.full
PRIMARY KEY
1a. Plants consisting of a flat dorsi-ventral thallus without differentiated stem and leaves, if leafy appendages present then multistratose at base or with small leaflike dorsal scales . . . (KEY A: THALLOID LIVERWORTS)
1b. Plants consisting of distinctive stem and leaves with regular shape; leaves unistratose throughout . . . (2)
2a. Leaves deeply dissected into 3 or more thread-like segments or hand-shaped with deeply dissected ciliate upper portions . . . (KEY B: CILIATE-LEAVED LIVERWORTS)
2b. Leaves entire, toothed, or 2, 3, or 4 lobed . . . (3)
3a. Leaves complicate-bilobed (consisting of 2 lobes folded over against one another or one lobe inflated and sac-shaped) . . . (KEY C: ECILIATE, COMPLICATE-BILOBED LIVERWORTS)
3b. Leaves simple, plane to concave, not folded . . . (4)
4a. Leaves incubous . . . (KEY D: ECILIATE, INCUBOUS, SIMPLE-LEAVED LIVERWORTS)
4b. Leaves succubous, obliquely to transversely inserted . . . (5)
5a. Leaf apices rounded to emarginate . . . (KEY E: ECILIATE, SUCCUBOUS, SIMPLE/ENTIRE-LEAVED LIVERWORTS)
5b. Leaf apices 2, 3, to 4 lobed . . . (KEY F: ECILIATE, SUCCUBOUS, SIMPLE/LOBE-LEAVED LIVERWORTS)
KEY A: THALLOID LIVERWORTS
(Plants consisting of a flat dorsi-ventral thallus without differentiated stem and leaves, if leafy appendages present then multistratose at base or with small leaflike dorsal scales)
1a. Plants aquatic or floating . . . 2
1b. Plants terrestrial . . . 3
2a. Plants floating (and occasionally stranded), spongy, forming fan-shaped colonies, with purplish-black ventral scales . . . Ricciocarpos natans
2b. Plants submerged, stringy or ribbon-shaped, forming loose colonies, without scales . . . Riccia fluitans complex
3a. Thalli with numerous and conspicuous urn-shaped structures (involucres) on dorsal surface . . . Sphaerocarpos
3b. Thalli with no urn-shaped structures on dorsal surface . . . 4
4a. Plants translucent, thin, delicate, lacking air chambers or air channels; rhizoids smooth; capsules developed on long setae . . . 5
4b. Plants opaque, thick, coarse, with internal air chambers or air channels (if absent than thalli very large, 1–2 or more cm wide); rhizoids pegged and smooth; capsules developed on short setae (but often on gametophoric stalks) . . . 11
5a. Thalli midrib gradually thinning to irregular to regular leaf-like lobes . . . Fossombronia
5b. Thalli with midrib distinct and abruptly thinning to plane or scalloped margins, or midrib indistinct and gradually thinning to plane or wavy margins, or midrib not present . . . 6
6a. Thalli consisting of rosettes with regular marginal lobes; stellate gemmae and flask-like gemmae bottles frequently present on dorsal surface; Nostoc colonies present in upper thallus . . . Blasia pusilla
6b. Thalli consisting of bifurcating branches with irregular to regular margins, gemmae not present, or if present not stellate or in special receptacles; Nostoc colonies not present . . . 7
7a. Thalli with hairs, sometimes confined to ventral surface or only on midrib . . . Metzgeria
7b. Thalli with no hairs on lamina or midrib . . . 8
8a. Midrib abruptly differentiated and very distinct, laciniate scales present on dorsal surface . . . Pallavicinia lyellii
8b. Midrib obscurely differentiated or absent; laciniate scales not present on dorsal surface . . . 9
9a. Thalli slender (less than 2 mm wide), variably and abundantly branched . . . Riccardia
9b. Thalli robust (more the 2 mm wide), not or dichotomously branched . . . 10
10a. Midrib absent; thallus greasy . . . Aneura
10b. Midrib present; thallus shiny . . . Pellia epiphylla var. epiphylla
11a. Thalli with receptacles containing gemmae on dorsal surface . . . 12
11b. Thalli without receptacles containing gemmae . . . 13
12a. Gemmae receptacles cup-like, forming a complete ring . . . Marchantia polymorpha
12b. Gemmae receptacles crescent shaped, forming an incomplete ring . . . Lunularia cruciata
13a. Upper thallus surface with conspicuous hexagonal pattern; pores elevated on a cone of whitish cells and easily seen with naked eye; aromatic when crushed . . . Conocephalum salebrosum/Type A
13b. Upper thallus surface without or with faint hexagonal pattern; pores variable and evident only with a hand lens or not present; not aromatic . . . 14
14a. Upper surface dark green, greasy in appearance, with whitish marginal hairs, without air pores; lower surface without scales; thalli large (0.8–3.0 cm wide); Appalachian in distribution . . . Dumortiera hirsuta ssp. hirsuta
14b. Upper surface blackish, brownish green to yellowgreen, dull in appearance, whitish marginal hairs lacking, with or without air pores; lower surface with scales; thalli small to medium-sized, (less than 1.0 cm wide), widespread in distribution . . . 15
15a. Thalli small (to 3.0 mm wide), forming rosettes and short, dichotomized individuals; air pores when present surrounded by undifferentiated cells; sporophytes embedded in thallus . . . Riccia, excluding the fluitans complex
15b. Thalli small to medium-sized (more than 2.5mm wide), in rosettes or coarsely branched ribbons; air pores present and surrounded by differentiated cells (slightly so in Corsinia); sporophytes produced external to thallus . . . 16
16a. Epidermal cells with bulging trigones . . . Reboulia hemisphaerica ssp. hemisphaerica
16b. Epidermal cells with no corner thickenings . . . 17
17a. Opening to air pores cruciate; innermost cells 4, pores subtended by a stack of cells appearing as a barrel in transverse section .... Marchantia quadrata
17b. Opening to air pores stellate to round, inner most cells 3–6, pores surrounded by a single layer of cells in transverse section . . . 18
18a. Pseudoperianths at maturity divided to form a whitish fringe of lanceolate segments . . . Asterella tenella
18b. Pseudoperianths at maturity entire, without a whitish fringe of lanceolate segments . . . Mannia
KEY B: CILIATE-LEAVED LIVERWORTS
(Leaves dissected more than half the leaf length into 3 or more ciliate lobes or filaments)
1a. Leaves with ciliate margins from a lower lamina . . . (2)
1b. Leaves divided to base (or nearly so) into 3–4 filaments . . . (3)
2a. Leaves divided for most of their length into 4–7 lobes, each 1–4 cells long . . . Trichocolea tomentella
2b. Leaves divided to half into 3–5 lobes, each 4 or more cells long . . . Ptilidium pulcherrimum
3a. Leaves divided to leaf base into uniseriate lobes . . . Blepharostoma trichophyllum
3b. Leaves divided deeply (but not to base) into 3–4 lobes each 2–4 cells wide at base . . . Kurzia sylvatica
KEY C: ECILIATE, COMPLICATE-BILOBED LIVERWORTS
(Leaves entire, toothed, or divided into 2, 3, or 4 lobes)
1a. Leaves with dorsal lobes smaller than the ventral lobes . . . (2)
1b. Leaves with dorsal lobes larger than the ventral lobes . . . (3 [Porellales])
2a. Ventral (larger) lobes ovate to rounded; perianths almost always flat, smooth, truncate and open at mouth; gemmae smooth . . . Scapania
2b. Ventral (larger) lobes oblong with parallel sides; perianths terete, plicate, contracted to mouth; gemmae smooth or angular . . . Diplophyllum apiculatum (var.?)
3a. Underleaves absent . . . (4)
3b. Underleaves present . . . (5)
4a. Leaf cells unipapillose or smooth; ventral lobes with 2–4-celled apical tooth; rhizoids attached to stem; perianth 5-angled, contracted to a short beak . . . Cololejeunea biddlecomiae
4b. Leaf cells smooth; ventral lobes entire; rhizoids attached to ventral lobes; perianth flat, truncate . . . Radula
5a. Ventral lobes elliptic, inflated, often with an apical tooth, attached to dorsal lobe along entire postical margin . . . (6 [Lejeunea complex])
5b. Ventral lobes helmet-shaped, lingulate, ligulate, or obovate, without apical tooth, attached to dorsal lobes by a stalk or by narrow postical band . . . (7)
6a. Underleaves unlobed or weakly notched; brownish secondary pigmentation often present . . . Cheilolejeunea
6b. Underleaves 2-lobed; brownish secondary pigmentation absent . . . Lejeunea
7a. Underleaves entire, unlobed . . . Porella
7b. Underleaves notched, bilobed . . . (8)
8a. Dorsal lobes apiculate; leaf cells thin-walled, trigones not present; plants of wet rocks . . . Jubula pennsylvanica
8b. Dorsal lobes rounded or rarely acute; leaf cells with trigones or evenly thick-walled; plants of dry rocks and tree trunks . . . Frullania
KEY D: ECILIATE, INCUBOUS, SIMPLE-LEAVED LIVERWORTS
(Leaves simple, incubous)
1a. Branching bi-pinnate to distinctly pinnate . . . Lepidozia reptans
1b. Branching dichotomous to irregular . . . (2)
2a. Leaves longer than wide, 2–3 notched at apex . . . Bazzania
2b. Leaves about as long as wide, entire to indistinctly 1–2 notched at apex . . . (3)
3a. Stems appearing flattened in section, usually of 4–6 cell rows dorsally, 4–6 cell rows ventrally, 5–6 cells high, laterally bounded on each side by 1 row of larger hyaline cells (to which leaves are attached); cuticle verruculose-striolate; lateral leaf apices regularly sharply 2-dentate; underleaves 2-fid, sometimes 4-lobed (bis-2-fid), divided to within 1(–2) cells of rhizoid initial area, lobes acuminate; basal underleaf outer margins uniformly armed with small, narrow, sharp teeth 1–2(–3) cells long, on each margin; oil bodies spheric to broadly ovoid, composed of minute spherules 1/3–1 µm . . . Asperifolia sullivantii
3b. Stems terete to elliptic in section, usually of 6–8(–14+) cell rows dorsally, 8–10+ cell rows ventrally, 7–9(–10) cells high, laterally bounded on each side by 2–3 rows of cells approximately the same size (to which leaves are attached); cuticle essentially smooth; lateral leaf apices entire or weakly 2-dentitulate; underleaves usually 2-lobed to entire, divided to within 2–6(–14) cells of rhizoid initial area, lobes when present broad and +/- obtuse to acute; underleaf margins entire or with short, broad, blunt teeth on one or both margins; oil bodies linear or ellipsoid, composed of large spherules 1.5–4 µm (minute in 1 species) . . . Calypogeia
KEY E: ECILIATE, SUCCUBOUS, SIMPLE/ENTIRE-LEAVED LIVERWORTS
(Leaves simple, succubous)
1a. Leaves with postical and antical margins strongly reflexed . . . Plagiochila
1b. Leaves with postical and antical margins plane to erect . . . 2
2a. Underleaves large, conspicuous under the dissecting microscope . . . 3
2b. Underleaves absent or consisting of tiny, lanceolate appendages of only a few cells . . . 5
3a. Underleaves deeply bifid; rhizoids restricted to small areas at base of underleaves . . . Chiloscyphus
3b. Underleaves lanceolate, without lobes; rhizoids occurring along stem . . . 4
4a. Stems with ventral stolons; leaves with or without border of thick-walled cells . . . Odontoschisma
4b. Stems never with ventral stolons; leaves without border of thick-walled cells . . . 5
5a. Leaves rectangular, longer than wide; perianth mouth abruptly contracted to short beak . . . Liochlaena lanceolata
5b. Leaves orbicular to ovate; perianth mouth plicate . . . 6
6a. Leaves often retuse; perianth mouth crenulate-denticulate to ciliate; female bracts laciniate or with basal teeth or cilia; perigynium lacking . . . Syzygiella autumnalis
6b. Leaves never retuse; perianth mouth crenulate; female bracts entire; perigynium present or lacking . . . 7
7a. Stem apices swollen, bearing endogenous gemmae; leaf cells with one large oil body; trigones absent . . . Endogemma caespiticia
7b. Stem apices similar to lower portions of stems, not swollen; without gemmae; leaf cells with numerous (3–9) oil bodies; with or without trigones . . . 8
8a. Leaves slightly wider than long; medial leaf cells 24µm wide or more; trigones present; perianth abruptly narrowed distally to a short, small beak . . . Solenostoma
8b. Leaves slightly longer than wide; medial leaf cells 25µm wide or less; trigones absent; perianth gradually narrowed or rounded to apex . . . Jungermannia pumila
KEY F: ECILIATE, SUCCUBOUS, SIMPLE/LOBE-LEAVED LIVERWORTS
(Leaves succubous, obliquely to transversely inserted with 2, 3, or 4 lobes)
1a. Leaves mostly 3 or 4-lobed . . . Schistochilopsis incisa
1b. Leaves 2-lobed, emarginate to deeply bilobed . . . 2
2a. Leaves retuse, emarginate, or divided less than 0.25 their length, sinus often broad . . . 3
2b. Leaves bilobed for more than 1/3 their length; sinus mostly narrow . . . 5
3a. Underleaves absent or consisting of only a few cells . . . Marsupella (in part)
3b. Underleaves large, visible under the dissecting microscope . . . 4
4a. Leaf lobes blunt; leaf cells with large bulging to confluent trigones . . . Nardia (in part)
4b. Leaf lobes acute; leaf cells thin-walled, without trigones . . . Harpanthus (in part)
5a. Plants isophyllous; underleaves similar to lateral leaves . . . Fuscocephaloziopsis (in part)
5b. Plants anisophyllous; underleaves much smaller (or lacking) than lateral leaves . . . 6
6a. Leaf lobes ending in a 1-seriate filament; postical leaf margin strongly curved forming an inflated sac; on rotting logs . . . Nowellia curvifolia
6b. Leaf lobes obtuse, acute, or acuminate; postical leaf margin similar to antical one; habitat various . . . 7
7a. Rhizoids restricted to small areas at base of underleaves . . . Lophocolea
7b. Rhizoids occurring along the stem, or not present . . . 8
8a. Underleaves 2-lobed with parallel margins, entire . . . Geocalyx graveolens
8b. Underleaves absent or present, variable in size, lanceolate and unlobed, or lanceolate and lobed or ciliate . . . 9
9a. Leaf lobes obtuse . . . 10
9b. Leaf lobes acute to acuminate . . . 11
10a. Underleaves lanceolate, often attached to lateral leaves on one side . . . Nardia (in part)
10b. Underleaves absent . . . Marsupella (in part)
11a. Plants thread-like to worm-like, very small (<1.0 mm wide) . . . 12
11b. Plants with erect to loosely spreading leaves, medium-sized (>1.0 mm wide) . . . 16
12a. Leaves horizonally to obliquely inserted, often dorsally decurrent; leaf lobes straight to connivent . . . 14
12b. Leaves transversely to obliquely inserted, not dorsally decurrent; leaf lobes straight . . . 15
13a. Stems without hyalodermis; leaf lobes straight; underleaves well developed lanceolate, sometimes attached to one lateral leaf . . . Harpanthus (in part)
13b. Stems with well-developed hyalodermis; leaf lobes connivent in some species; underleaves absent or only developed on fertile stems . . . 14
14a. Leaves longer than wide; leaf lobes erect (not connivent), sinus acute; brownish to vinaceous pigmentation present in some species . . . Cephalozia bicuspidata
14b. Leaves isodiametric, as wide as long; leaf lobes often connivent, sinus obtuse; pigmentation lacking . . . Fuscocephaloziopsis (in part)
15a. Leaves bilobed ½ or more their length . . . Cephaloziella
15b. Leaves bilobed less than ½ their length . . . Marsupella (in part)
16a. Plants flaccid, succulent, pale- to dark-green; leaf cells without oil bodies; underleaves small, inconspicuous, hidden in rhizoids; occurring on west coast in subalpine-alpine seepage zones . . . Fuscocephaloziopsis (in part)
16b. Plants thin (not succulent), various shades of green to brownish; leaf cells always with oil bodies; underleaves absent to well-developed; widespread in distribution . . . 17
17a. Leaf insertion transverse; leaves cupped to caniculate with incurved lobes . . . Marsupella (in part)
17b. Leaf insertion oblique to sub-transverse; leaves erect-spreading with erect lobes . . . 18
18a. Leaf cells thin-walled, >(30)35 µm; plants commonly with masses of pale green, terminal gemmae . . . Schistochilopsis incisa
18b. Leaf cells <30 µm, collenchymatous or thick-walled, trigones often present; plants with orange, reddish, brown, or purplish gemmae in small terminal clusters or on tips of leaf lobes, or absent . . . Isopaches bicrenatus
Required Keys to Genera
Key to Aneura
Key to Bazzania
Key to Calypogeia
Key to Cephaloziella
Key to Cheilolejeunea
Key to Chiloscyphus
Key to Fossombronia
Key to Frullania
Key to Fuscocephaloziopsis
Harpanthus?
Key to Lejeunea
Key to Lophocolea
Key to Mannia
Key to Marchantia polymorpha
Marsupella?
Key to Metzgeria
Nardia?
Key to Odontoschisma
Key to Plagiochila
Key to Porella
Key to Radula
Key to Riccardia
Key to Riccia (excl. fluitans complex)
Key to Riccia fluitans complex
Key to Scapania
Key to Solenostoma
Key to Sphaerocarpos
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