adapted from: How to Know the Mosses and Liverworts H.S. Conard; Wm.C. Brown Company; 1979.
Genera in red are not known from the Northeast. Additional usage notes at bottom.
1a - Plants thalloid, with 1 chloroplast per cell; sporophyte long rod-like, splitting into 2 parts above as it grows ... Antherocerotae - Hornworts
1b - Plants thalloid or leafy with more than 1 chloroplast per cell; sporophyte with a spherical or ellipsoidal capsule ... 2
2a - Plants strongly flattened, thalloid, without distinction between stem and leaf ... 3
2b - Plants slightly flattened, distinctly divided into stem and leaf ... 5
3a - Plants with opaque thallus divided into epidermis, loose tissue beneath the epidermis containing air spaces, and a lower solid parenchyma-like tissue rhizoids of 2 kinds,1 with smooth wall and 1 with peg-like thickenings on inner wall; sporophytes with capsules not dividing regularly into 4 valves ... Marchantiales - Complex Thalloid Liverworts
3b - Plants with a translucent or transparent thallus, inner tissue homogenous; rhizoids all smooth on internal wall; sporophytes with capsule dividing regularly into 4 valves or dehiscing irregularly and retained in a sac-like structure ... 4
4a - Thallus appearing as small rosette or scales with surface covered with pear-shaped sacs (involucres) each containing a capsule that dehisces irregularly; no elaters in capsule ... Sphaerocarpales
4b - Thallus ribbon-shaped, not covered on upper surface with pear-shaped sacs; capsules regularly splitting into 4 lobes; elater present ... Metzgeriales - Simple Thalloid Liverworts
5a - Archegonia on dorsal surface, not limiting growth of thallus, several developing, one behind the other on same plant; surrounded at base by campanulate pseudoperianth; sporophytes with capsule not rupturing into 4 regular valves ... Fossombronia
5b - Archegonia at end of thallus, terminating its further growth, with only 1 developing into a sporophytes, usually surrounded a base by perianth; sporophyte with capsule rupturing regularly into 4 valves ... 6
6a - Rhizoids present; wall of capsule 2-10 cells thick ... Jungermanniales Leafy Liverworts
6b - Rhizoids absent; when present capsule with wall 1 cell thick ... 7
7a - Leaves typically divided into 2-3 segments to base ... Takakiales
7b - Leaves unlobed ... Haplomitrium
1a - Plants aquatic submerged, with long erect stem and 1 longitudinal wing-like expansion on vein ... Riella
1b - Plants terrestrial, prostrate or nearly so, with no wing-like expansion of vein ... Sphaerocarpus
1a - Capsules erect 1-3cm long becoming black after splitting ... 2
1b - Capsules horizontal, short, slightly projecting form margins of thallus ... Notothylas orbibularis
2a - Spores black ... Anthoceros macounii, punctatus
2b - Spores yellow ... Phaeoceros carolinianus, laevis
1a - Leaves deeply divided for 0.6-0.9 their length into many filiform segments 1-2 cells broad or into cilia ... 2
1b - Leaves entire, toothed or divided at tip into 2, 3 or 4 lobes ... 6
2a - Plants robust ... 3
2b - Plant minute, filiform and slender ... 4
3a - Plants white-green; cells without trigones ... Trichocolea tomentella
3b - Plants green to fulvous or red-brown; cells with distinct trigones ... Ptilidium ciliare, pulcherrimum
4a - Leaf segments formed of delicate elongated cells (50-100µ); shiny when dry ... Telaranea longifolia
4b - Leaf segments formed of short rigid cells (< 50 µ); dull when dry ... 5
5a - Basal part of divisions 2 cells wide ... Kurzia pauciflora, sylvatica
5b - Basal part of divisions 1 cell wide ... Blepharostoma trichophyllum
6a - Plants robust; leaves bilobed more or less falcate-secund, with bifurcate vitta of elongated cells extending to or beyond middle of lobes ... Herbertus
6b - Plants not as above; if leaves bilobed, bifurcate vitta absent ... 7
7a - Leaves transversely attached or succubus; attached obliquely so that the edge of the leaf on the upper surface of the edge of the leaf on the upper surface of stem is attached nearer the base of the stem than the lower edge; thus the leaf slopes toward the apex of the stem ... 8
7b - Leaves incubous; attached obliquely to the stem so that the edge of the leaf on the upper surface of the stem is attached nearer the apex of the stem than the lower edge; thus the leaf slopes toward the base of the stem ... 39
8a - Leaves entire and unlobed; underleaves absent or considerably smaller than leaves ... 9
8b - Leaves lobed or margins with distinct teeth ... 16
9a - Plants bearing leafless stolons; leaves often marginated with thicker walled cells ... Odontoschisma [7]
9b - Plant without leafless stolons ... 10
10a - Cells of leaf middle large, >45 µm wide, with large coarse, nodose trigones ... Mylia anomala, taylori
10b - Cells of leaf middle smaller, < 36 µm wide, trigones small or absent ... 11
11a - Rhizoids restricted to small areas at bases of large lanceolate or bifid underleaves ... 12
11b - Rhizoids scattered over stem; underleaves absent or small and inconspicuous ... 13
12a - Perianth triangular, split in 3 at top, overtopped by the larger, obovate calyptra (archegonium) when sporophyte emerges, borne on short branch; underleaves present, conspicuous, 2-lobed; antheridia in axils of leaves in groups along stem ... Chiloscyphus*
12b - Similar to above, but calyptra remaining deep within perianth, which terminates main shoot; antheridia just below perianth ... Lophocolea [3]
13a - Underleaves present, small, undivided, lanceolate; leaves orbicular ... Nardia [3]
13b - Underleaves lacking or divided into several cilia ... 14
14a - Leave succubous, long-decurrent on upper side of stem with margins turned back; underleaves minute but distinct, formed of 2-several short cilia tipped by slime papillae ... Plagiochila austinii, porelloides
14b - Leaves not as above; underleaves lacking or present only as an unlobed vestige ... 15
15a - Mouth of perianth contracted, and fringed with many-celled hairs ... Syzygiella autumnalis
15b - Mouth of perianth plaited but not fringed ... Jungermannia*; Solenostoma
16a - Leaves complicated-bilobed, smaller antical (upper) lobe bent over dorsal side of larger postical (lower) lobe; keel between lobes sharp; underleaves absent ... 17
16b - Leaves not complicate-bilobed ... 18
17a - Postical (large) lobe oblong-lanceolate; perianth cylindric and furrowed ... Diplophyllum [4]
17b - Postical (large) lobe rounded-ovate; perianth with wide flattened mouth ... Scapania [19]
18a - Leaves transversely inserted on stem ... 19
18b - Leaves succubously inserted and thus more or less obliquely oriented ... 27
19a - leaves 3-4 lobes ... 20
19b - Leaves mostly bilobed ... 23
20a - Most leaves 4-lobed, underleaves very large, usually 2-lobed ... 21
20b - Most leaves 3-lobed, underleaves small or absent ... 22
21a - Underleaves large, almost as long as leaves ... Tetralophozia setiformis
21b - Underleaves smaller, < half length of leaves ... Lophozia*
22a - Underleaves small; antical lobe of leaves clearly larger; antical end of leaf insertion oblique, running down stem ... Lophozia*
22b - Underleaves absent; antical lobe of leaves smaller or equal to others; antical half of leaf insertion transverse or running up towards stem apex ... Tritomaria*
23a - Lobes of leaves ciliate ... Nowellia curvifolia
23b - Lobes of leaves obtuse, acute, or rounded ... 24
Anthelia juratzkana; Hygrobiella laxifolia; Gymnomitrion concinnatum, corallioides; Prasanthus suecicus would likely key here or the next couplets. All are minute to small (~0.5mm wide), rare and arctic/subalpine/alpine.
24a - Leaf lobes acute or sub acute, somewhat unequal, antical smaller; leaves loosely complicate; vinaceous to red or purple gemmae present on leaves; plants usually robust, 0.7-2.5mm wide ... Anastrophyllum*
24b - Leaf lobes equal or nearly so, not at all complicate; gemmae absent or smoothly ovoid or ellipsoidal ... 25
25a - Leaf cells collenchymatous, trigones often bulging; underleaves and gemmae absent; shoots 0.2-3.0 mm wide ... Marsupella [6]
25b - Leaf cells not collenchymatous, trigones absent; leaves bilobed; underleaves present; gemmae often present; shoots < 1.0mm wide ... 26
26a - Cells very small, 6-15µ wide at base of lobes; outer cells of stem without large pellucid cells ... Cephaloziella [11]
26b - Cells larger, 12-40µ wide at base of lobes; outer cells of stem large and pellucid ... Cephalozia* [3]; Fuscocephaloziopsis [7]
27a - Underleaves of sterile shoots present, well developed, often large ... 28
27b - Underleaves of sterile shoots absent or poorly developed ... 34
28a - Rhizoids restricted to bases of underleaves; underleaves bifid, usually with 1 or 2 teeth on outer margins ... Lophocolea [4]
28b - Rhizoids scattered over lower surface of shoots ... 29
29a - Leaf margins dentate but not lobed, rarely entire ... Plagiochila austinii, porelloides
29b - Leaf margins entire except at apex that is clearly bilobed ... 30
30a - Underleaves unlobed, ovate to lingulate to ovate-lanceolate ... 31
30b - Underleaves bilobed, ciliate or dentate ... 33
31a - Cells equally thick-walled ... Odontoschisma (Cladopodiella) fluitans, francisci
31b - Cells thin-walled with conspicuous, often bulging trigones ... 32
32a - Branches mainly ventral in origin ... Harpanthus [3]
32b - Branches all lateral ... Nardia [3]
33a - Underleaves bifid almost to base in 2 parallel, lanceolate segments ... Geocalyx graveolans
33b - Underleaves not as above, more or less ciliate or dentate ... Lophozia*
34a - Leaves (at least some) >3 lobed, or irregularly lobed or bearing several to many teeth ... 35
34b - Leaves uniformly and simply bilobed ... 36
35a - Leaves with filiform lobes or spinose dentate on margins ... Plagiochila austinii, porelloides
35b - Leaves bearing 3-4 subequal lobes without accessory teeth ... Barbilophozia*
36a - Most branches, or at least sexual branches, ventral in origin; leaf cells non-collenchymatous ... 37
36b - Branches uniformly lateral in origin, plants usually black ... Gymnocolea inflata
37a - Outer cells of stem large, pellucid; underleaves absent ... Cephalozia* [3]; Fuscocephaloziopsis [7]
37b - Outer cells of stem small, opaque ... 38
38a - Plants > 0.5mm wide; leaves with rounded or obtuse lobes ... Cladopodiella
38b - Plants very small, usually < 0.5mm wide; leaves with acute to subacute lobes ... Cephaloziella
39a - Leaves not complicate-bilobed ... 40
39b - Leaves complicate-bilobed ... 42
40a - Leaves divided to middle in 3-4 lobes ... Lepidozia reptans
40b - Leaves 2-3 dentate at apex or entire ... 41
41a - Leaves 2-3 dentate at apex; plants opaque, green to brown ... Bazzania [3]
41b - Leaves entire to minutely bidentate at apex; plants generally pellucid, pale to blue-green or gray-green ... Calypogeia [7]; Eocalypogeia schusteriana
42a - Underleaves absent ... 43
42b - Underleaves present ... 44
43a - Rhizoids originating on ventral lobes; plants opaque, green ... Radula [3]
43b - Rhizoids on stem; plants pellucid or yellow-green ... Cololejeunea biddlecomiae
44a - Underleaves unlobed ... 45
44b - Underleaves bilobed ... 49
45a - Lobule lingulate or oblong, lying parallel with stem; large plants 2.5-5mm wide ... Porella pinnata, platyphylla
45b - Lobule inflated, lying parallel with posterior leaf margin, attached to it by long keel; minute to small plants, 0.3-2.5mm wide ... 46
46a - Margins of lobule with 4-6 minute teeth ... Ptychocoleus
46b - Margin of lobule with 1-2 teeth at or near apex, or entire ... 47
47a - Plants gray-green ... Cheilolejeunea clypeata
47b - Plants fuscous to black-green ... 48
48a - Mature plants closely appressed to substrate, shiny & flat when dry ... Lopholejeunea
48b - Mature plants ascending or suberect, dull; leaves convolute when dry ... Mastigolejeunea
49a - Lobule conspicuous, attached by very narrow stalk-like base, appearing free from stem; plants opaque, deep green to red-brown; underleaves inserted on >4 rows of stem cells ... 50
49b - Lobules usually broadly attached to stem (or obsolete); plants usually pale green to yellow-green; underleaves attached to only 2 rows of large ventral stem cells ... 51
50a - Plants dark green; dorsal lobe pointed; cell walls thin; leaf subtending branch partly attached to branch ... Jubula pennsylvanica
50b - Plants black to red-brown or green; dorsal lobe usually not pointed; cell walls usually thick, with conspicuous trigones and often with bead-like thickenings along walls (intermediate thickenings); leaf subtending branch attached only to subtending branch attached only to stem ... Frullania [12]
51a - Underleaves widest near middle with lobes nearly erect or connivent ... 52
51b - Underleaves with lobes uniformly and distinctly divergent, thus widest at base ... 55
52a - Plants brown tinged, shiny when dry; apical tooth of lobule prominent; with 1-several large paracysts at base ... Ceratojeunea
52b - Plants green not brown tinged; apical tooth of lobe usually small; paracysts usually absent ... 53
53a - Leaves clearly caducous (falling off stem); perianth strongly dorsiventrally compressed ... Rectolejeunea
53b - Leaves persistent; perianth not dorsiventrally compressed ... 54
54a - Leaves always broadly rounded at apex; cells with vestigial to small trigones and few or without intermediate thickenings ... Lejeunea cavifolia, cavifolia; Microlejeunea ulicina
54b - Leaves apiculate or mucronate; cells with large trigones and numerous intermediate thickenings ... Crossotolejeunea
55a - Underleaves as many as lateral leaves; lobule with long filiform tooth ... Diplasiolejeunea
55b - Underleaves half as many as lateral leaves; lobules with small1-celled apical tooth ... Depanolejeunea
1a - Air pores visible without lens, each in polygonal area; capsules borne on underside of umbrella-shaped receptacle; with spirally banned elaters among spores; walls of capsules with ring-shaped thickenings ... 8
1b - Air pores absent, or visible only with strong lens ... 2
2a - Plants submerged, floating or in circular rosettes on very wet ground; air pores not visible with hand lens; capsules embedded in plant with no elaters among rough spores ... 3
2b - Plants on moist or dry rocks or banks, rarely in neat rosettes; capsules borne on underside of umbrella-shaped receptacle ... 4
3a - Lobes of thallus 5-10mm wide, with air spaces in 3-4 irregular layers; in rosettes 2-3cm across on muddy shores or floating in triangular pieces bearing many scales beneath; plants with distinct sharp median groove throughout length of thallus ... Ricciocarpus natans
3b - Lobes 1-3mm wide, with air chambers in 1-2 layers or with mere chinks between chains of upper cells; plants without sharp median groove, or with groove confined to tip of thallus ... Riccia [10]
4a - Thallus without or with only vestigial pores ... Dumortiera
4b - Thallus with pores ... 5
5a - Cell walls radiating from pores strongly thickened, giving pore star-like (stellate) appearance ... Clevea hyalina
5b - Pores absent or not stellate in appearance ... 6
6a - Cells of epidermis with thin walls and large bulging trigones; pores inconspicuous ... 11
6b - Trigones of epidermal cell small, not bulging ... 7
7a - Cells around pores in 2-3 concentric rows, thick-walled; cells of epidermis collenchymatous (walls thickened all around and at corners); white scales around base and summit of stalk ... Mannia [3]
7b - Cells around pores irregular, thin-walled; cells of epidermis not collenchymatous; stalk of umbrella naked at both ends. capsule surrounded by several scales, remnants of tubular pseudo-perianth ... Asterella tenella
8a - Thallus with open or half-cups of dish-shaped gemmae; archegonia (and sporophytes) on underside of long-fingered umbrellas with 4-9 fingers ... 9
8b - Thallus without gemmae, and without marginal scales on underside ... 10
9a - Gemmae cups round fringed; female umbrella 9-lobed; thallus with thin scales along margin beneath; air pores elliptic ... Marchantia polymorpha
9b - Gemmae in half-cups; female umbrellas 4-lobed; thallus without marginal scales beneath; found only in greenhouses and sterile ... Lunularia
10a - Air pore on low mound of colorless cells; antheridia in warty spot on thallus; sporophytes beneath cone-shaped umbrella ... Conocephalum salebrosum
10b - Air pores circular surrounded by low cylinder of cells; antheridia and sporophytes on upraised scalloped umbrellas ... Marchantia quadrata
11a - Pores surrounded by4-5 concentric rows of thick walled cells ... Reboulia hemisphaerica
11b - Pores not surrounded by concentric rows of thick walled cells ... Targionia
1a - Plants divides into stem and into leaves, rhizoids purple ... Fossombronia [4]
1b - Plants thallose or shallowly lobed ... 2
2a - Plants shallowly lobed, with scattered lumps of blue-green algae imbedded in thallus; gemmae present in bottle-shaped containers or with tiny star-shaped gemmae ... Blasia pusilla
2b - Margins of thallus wavy or even, but not shallowly lobed ... 3
3a - Midrib well defined, bulging like a cord along lower side of plant, rest of thallus only 1 cell thick ... 4
3b - Midrib ill-defined, merely the gradually thickened central part of the plant, thallus only 1 cell thick at margin if at all ... 6
4a - Plant 1-2mm wide, much longer than wide, of very even width, forking; sex organs underneath ... Metzgeria/Apometzgeria [5]
4b - Plant 3-4mm wide, often irregularly wavy; sex organs on upper side along midrib ... 5
5a - Midrib with central strand of small, thick-walled cells ... Pallavicinia lyellii
5b - Midrib without central strand ... Moerckia flotoviana
Aneura pinguis, sharpii will key here; sessile 1-celled slime papilae and colorless rhizoids will distinguish sterile plants; fertile plants are much different.
6a - Plant 4-16mm wide, usually crowded in wide (10-50mm) patches; elaters attached at base of capsule, on moist shaded ground ... Pellia/Apopellia [3]
6b - Plant 1-5mm wide, variously lobed or branched, in very wet places or in shallow water ... Riccardia [5]
adapted from: How to Know the Mosses and Liverworts H.S. Conard; Wm.C. Brown Company; 1979.
This is an edited transcription from the book of the liverwort key to genus.
Genera in red are not known from the Northeast.
Where species are indicated, those are species known from the Northeast. Number in brackets is the number of sensu lato species in the Northeast.
* indicates that the genus has been split or lumped since 1979. See the Annotated Checklist for species and synonyms.
The following lists some of the genera that have been split since this was originally published:
• Anastrophyllum >> Crossocalyx, Sphenolobus
• Lophozia >> Barbilophozia, Isopaches, Lophoziopsis, Mesoptychia, Neoorthocaulis, Obtusifolium, Schistochilopsis, Schljakovia, Tritomaria
• Jungermannia >> Liochlaena, Solenostoma
Errors or improvements? Email Jeff at info@DigitalNaturalist.info.
last update 2025-Jul-03