BFNA Title: Asterella
Asterella - Aytoniaceae
XX. ASTERELLA Palisot de Beauvois, Lam. Dist. Sci. Nat. 3: 257. 1805 · [aster + ‑ella, little star, for shape of female receptacle]
Marie L. Hicks
Plants in depressed interwoven patches or partial rosettes, simple or forked; branching primarily dichotomous or with intercalary branches, arising ventrally by narrow stipes, clavate, cordate or elongate; apical innovations occasional, forming cordate or elongate segments. Thalli 20‑‑30 ´ 1.5‑‑6 mm, margins plane or ascending, often undulate, not crenulate; dorsal side green with purplish margins, underside purple; drying plant margins curling upward and inward exposing the purple underside, appearing as blackish‑purple tubes; dorsal epidermis not to very slightly areolate, firm, persistent; cell walls thin to moderately thick‑walled, trigones small or absent; oil cells scattered; air pores simple, the openings surrounded by 1‑‑3 tiers of 4‑‑8 scarcely differentiated cells; mid‑ventral thallus 8‑‑15 cells thick, of compact parenchymatous layers forming a broad keel gradually diminishing in thickness to the margins; dorsal spongy layers 2‑‑4 cells thick, containing air chambers lacking photosynthetic filaments; oil cells scattered; rhizoids dense, some smooth, some with internal pegs; ventral scales purple, in 2 rows, lunate to ovate with scattered oil cells; appendages hyaline, white or purplish, 1‑‑2(‑‑3) per scale, triangular to acuminate, not or scarcely constricted at base. Specialized asexual reproduction absent. Sexual condition monoecious or dioecious; androecia sessile, often purplish, in dorsal patches of papillae or in discrete thickened pads surrounded by small subulate scales; the position of androecia in some monoecious species may vary from posterior to the gynoecial stalks (paroecious) to apical on dichotomous branches or short intercalary branches (autoecious) or antheridial papillae occasionally form a mid‑dorsal streak; gynoecia terminal on thalli; stalks 0.4‑‑5 cm with one rhizoid furrow, with or without hairlike scales at bases and/or apices; carpocephala bell‑shaped, domed, ovate or umbonate with air pores on upper surface, developing 1‑‑4 lobes below, each containing one sporophyte surrounded by an exerted, white to purplish, pleated conical pseudoperianth that splits into 8‑‑16 apically connate linear segments, becoming free with age in some species. Sporophyte capsule spherical, irregularly circumscissile; spores areolate, the areolae bordered by partitions appearing in silhouette as a wing; elaters 120‑‑250 ´ 12‑‑15 µm, 1‑‑3 spiral.
Species ca. 80 (8 in the flora): on soil worldwide.
SELECTED REFERENCES Evans, A. M. 1920. The North American Species of Asterella. Contrib. U.S. Nat. Herbarium. 20(8): 247-‑312. Schuster, R.M. 1992. The Hepaticae and Anthocerotae of North America. Vol. 6. Chicago.
1. Gynoecial stalks naked, without hairlike scales at bases or apices; plants paroecious or autoecious .
2. Spores dark brown; southwestern ... 1. Asterella palmeri
2. Spores yellow or pale brown; eastern or boreal.
3. Androecia distinct, paroecious or autoecious; pseudoperianth segments free at maturity; boreal‑alpine .....2. Asterella gracilis
3. Androecia inconspicuous, of few papillae at base of gynoecial stalk; pseudoperianths conical, segments not free; east of 100th meridian .....3. Asterella tenella
1. Gynoecial stalks with hairlike scales at bases or apices (or both).
4. Thallus branches primarily lateral intercalary; androecia on short stipitate branches, occasionally on main thallus; southwestern.
5. Carpocephala upper surfaces with fingerlike protruberances; stalks with hairlike scales at bases and apices; Texas ......4. Asterella echinella
5. Carpocephala upper surfaces smooth or with low tubercules; stalks with hairlike scales at apices, none at bases; west coast ... 5. Asterella bolanderi
4. Thallus branches primarily dichotomous; androecia on main thalli or its dichotomous branches.
6. Carpocephala pale green with spreading lobes and long pale hairlike scales beneath, base of stalk naked; plants dioecious; west coast .. 6. Asterella californica
6. Carpocephala green or purplish, the lobes directed downward; stalks with hairlike scales at base; boreal.
7. Spores and elaters purple; stalks with hairlike scales beneath carpocephala and at base ..7. Asterella lindenbergiana
7. Spores yellow or pale brown; without hairlike scales beneath carpocephala; conspicuous white scale appendages forming cluster at apices of thallus branches ... 8. Asterella saccata
1. Asterella palmeri (Austin) Underwood, Bot. Gaz. 20: 63. 1895
Fimbriaria palmeri Austin, Bull. Torrey Bot. Cl. 6: 47. 1875
Plants green with purplish undulate margins and deep purple ventral side; branching dichotomous or thalli simple; intercalary lateral branches rare. Thalli 5‑‑10 ´ 2‑‑4 mm; epidermis smooth, cells mostly 30 x 25 µm, thin‑walled, with very small trigones, oil cells absent; air pores surrounded by 1‑‑2 tiers of 5‑‑6 cells with slightly thickened radial walls; ventral scales imbricate, deep purple with scattered oil cells; appendages 1‑‑2, purplish or hyaline, subulate to acuminate, often with few small marginal teeth, extending slightly beyond thallus margins at apices. Sexual condition paroecious, occasionally autoecious; androecia small dorsal group of papillae at posterior base of gynoecial stalks or occasionally forming mid‑dorsal streaks of papillae; gynoecia terminal on principal thalli; stalks naked, without hairlike scales at bases or apices, 1‑‑2 cm, purplish; carpocephala high‑domed to ovoid or conical, about 4 mm high, 2.5 mm wide, with 3‑‑4 lobes directed downward; pseudoperianths white, conelike, cleft 1/3‑‑1/2 the length into 8‑‑10 or more segments with attached apices. Sporophyte capsules dark brown; spores dark brown, 60‑‑80 µm; elaters curved, brown, 2‑spiral, 150‑‑180 µm.
Capsules mature Feb.--Apr. Soil banks in rather dry situations; sw Calif.; Mexico (Baja California Norte).
This species can be recognized when fruiting by the dark brown spores. Other species have yellow or purple spores except A. echinella which has pale brown spores and is unlikely to be confused with A. palmeri because of the strongly tuberculate carpocephala of the former.
2. Asterella gracilis (F. Weber) Underwood, Bot Gaz. 20: 61. 1895
Marchantia gracilis F. Weber, Hist. Musc. Hep. Prodr. 105. 1815
Plants green with deep purplish undersides and margins; branching dichotomous, ventral intercalary branches occasional. Thalli 5‑‑15 ´ 1‑‑3 mm; epidermis smooth, cells thin‑walled, 25‑‑35 ´ 25‑‑28 µm, trigones small or absent, oil cells few, scattered; air pores surrounded by 2‑‑3 tiers of 6‑‑8 scarcely differentiated cells; ventral scales purplish with few oil cells; appendages 1‑‑2, lanceolate. Sexual condition paroecious; androecia purplish groups of papillae posterior to bases of gynoecial stalks, occasionally on separate branches, then ovate; gynoecia terminal on dichotomous branches; stalks 1‑‑3 cm, naked above, bases purplish with inconspicuous, subulate, deciduous scales; carpocephala hemispheric, 2‑‑3 mm across, upper surface smooth, becoming low tuberculate on drying, 2‑‑4 lobed below; pseudoperianths short, directed obliquely downward, the segments usually 8, free with age. Sporophyte capsules yellowish‑brown; spores yellow, 60‑‑85 µm; elaters yellowish, 2‑‑3 spiral, 150‑‑200 µm.
Capsules mature Apr.--Aug. Moist soil over rock, usually calcareous in Arctic‑alpine areas; Greenland, Alta., B.C., N.W.T., Nun. (Baffin Island); Alaska, Ariz., Calif., Colo., Mich., Minn., Mont., N.Mex., Utah, Wyo; Europe; Asia.
This plant has been erroneously known in North America as A. Ludwigii (Schwaegrichen) Underwood and was listed as such in past publications. According to R. Grolle (1975) the type of A. ludwigii is Mannia triandra.
3. Asterella tenella (Linnaeus) Palisot de Beauvois, Lam. Dict. Sci. Nat. 3:257. 1805
Marchantia tenella Linnaeus, Sp. Pl. 1137. 1753
Plants green with purplish undulate margins and purplish underside; branching dichotomous, rarely with intercalary branches. Thalli 6‑‑15 ´ 1.5‑‑3 mm; epidermis smooth, cells 25‑‑40 ´ 20‑‑25 µm, walls not to slightly thickened, trigones absent or small; oil cells few, scattered; air pores surrounded by 1‑‑3 tiers of 4‑‑6 scarcely differentiated cells; ventral scales purple with few scattered oil cells; appendages 1‑‑2, white, lanceolate. Sexual condition paroecious, androecia of inconspicuous papillae at posterior base of gynoecial stalk; gynoecia in apical notch of main thalli; stalks naked, often purplish, 1‑‑3 cm, without hairlike scales at bases or apices; carpocephala bell shaped, smooth, 3‑‑4 mm across, lobes 3‑‑4, short, directed downward; pseudoperianths white or purplish, conical, of 8‑‑12 segments, connate at their apices, occasionally free with age. Sporophyte capsules pale yellowish brown; spores yellow, 85‑‑100 µm; elaters yellowish‑brown, 2‑spiral, 150-‑250 µm.
Capsules mature Mar.--June. Soil over rock near streams; low elevations; Ont.; Que., Ala., Ark., Conn., D.C., Ga., Ill., Ind., Kans., Ky., La., Maine, Md., Mass., Miss., Mo., N.H., N.J., N.C., N.Y., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va.
This species is common in e North America extending westward to Kansas; it has not been found west of the 100th meridian.
4. Asterella echinella (Gottsche) Underwood, Bot. Gaz. 20: 62. 1895
Fimbriaria echinella Gottsche, Dansk. Vid. Sellsk. Skrift. V 6: 367 1863
Plants green above with deep purple pigmentation along margins and below; branching intercalary from a simple or dichotomous main thallus; lateral‑ventral branches frequent, arising by narrow stalks, the distal portions often obcordate; apical innovations also occur. Thalli 10‑‑30 ´ 2‑‑3 mm with margins often undulating and ascending; epidermis smooth, cells 30‑‑50 ´ 30‑‑35 µm with slightly thickened walls, without distinct trigones; air pores surrounded by 1‑‑2 tiers of 6‑‑8 cells; ventral scales deep purple with scattered oil cells; appendages 1‑‑2, white or purplish tinged, subulate to acuminate, 3‑‑4 cells wide, slightly narrowed at base. Sexual condition autoecious, male branches short, obcordate, sometimes innovating apically; androecia terminal, deep purple, oblong, ovate or subcordate, thickened, the margins with small subulate scales; gynoecia on principal branches or short innovative branches; stalks 0.5‑‑1.5 cm, reddish tinged with hairlike scales at apices and sparse scales at bases; carpocephala domed, 2‑‑3 mm wide with conspicuous finger‑like tubercules on upper surfaces, 1‑‑3 lobed below; pseudoperianths white to slightly purple, of 8‑‑10 segments, connate at apices. Sporophyte capsules brownish; spores yellowish to pale brown, 60‑‑100 µm, elaters brown, 1‑‑2 spiral, 140‑‑200 µm.
Capsules mature May. Soil over rocks, often calcareous, near streams; Tex.; Mexico.
The conspicuous finger‑like tubercules on carpocephala distinguish this species from others in the flora. Asterella echinella was listed by W. S. Sullivant (1856) and L. M. Underwood (1884) as A. elegans, a plant of Mexico. Subsequently R. Stotler and B. Crandall-Stotler (1977) listed it as A. elegans subsp. echinella (Gottsche) Del Rosario in error. Thus far, A. elegans has not been found north of Mexico.
5. Asterella bolanderi (Austin) Underwood, Bot. Gaz. 20: 61 1895
Fimbriaria bolanderi Austin, Proc. Acad. Sci. Phila. 21: 230 1869
Plants green above, deep purple below and along margins, which are undulate and slightly ascending; branching by numerous short intercalary lateral branches that arise beneath main thallus; dichotomous branches few. Thalli 10‑‑30 ´ 2‑‑4 mm; epidermis smooth, cells 30‑‑40 ´ 20‑‑30 µm, the walls slightly thickened, trigones small or lacking, oil cells few, scattered; air pores scarcely elevated, with 2‑‑3 tiers of 7‑‑8 cells around the opening; ventral scales deep purplish‑red with scattered oil cells; appendages 1‑‑2 purplish or hyaline, lanceolate to acuminate. Sexual condition autoecious, sex organs on short latero‑ventral intercalary branches; androecia on very short clavate branches, the androecia ovate, without surrounding scales; gynoecia on short, obcordate branches, stalks reddish, 1‑‑3 cm with sparse hair‑like scales at apices, few or none at bases; carpocephala high domed and bell‑shaped, 2.4‑‑4 mm across, usually 4‑lobed, the lobes directed obliquely downward; pseudoperianths white or reddish tinged, 10‑‑12 cleft, the segments connate at apices. Sporophyte capsules yellowish brown; spores yellow to pale brown, 65‑‑100 µm; elaters yellow to pale brownish, 2(‑‑3)‑spiral, 150‑‑220 µm.
Capsules mature Mar.--May. Soil of shaded banks; Calif., sw Oreg.
The presence of frequent, short, intercalary branches and paucity of dichotomous branching distinguishes this species from others of the genus in the flora. The principal thalli often curl when dry, exposing the dark purple underside. Asterella bolanderi subsp. acrogyna R. M. Schuster named from a single Texas collection (R. M. Schuster 1985), was a specimen of Reboulia, later treated (R. M. Schuster 1992) as Reboulia hemisphaerica subsp. acrogyna (R. M. Schuster) R. M. Schuster.
6. Asterella californica (Underwood) Underwood, Bot. Gaz, 20: 60 1895
Fimbriaria californica Underwood, Bull. Ill. Lab. Nat. Hist. 2: 41 1884
Plants pale green to green dorsally with purple ascending margins and dark purple undersides, edges tending to curl upward exposing the dark underside when dry; branching dichotomous, seldom with intercalary branches. Thalli 10‑‑25 ´ 4‑‑10 mm; epidermis faintly areolate, cells 50 ´ 30 µm with thin walls, trigones small or lacking, oil cells few, scattered; air pores surrounded by 2‑‑3 tiers of 6‑‑7 cells with slightly thickened radial walls; ventral scales purplish with few oil cells; appendages 1‑‑3, hyaline, triangular‑acuminate. Sexual condition dioecious; separate male plants often intermingled with female plants; androecia dorsal, forming thick, distinct ovate or elongate patches, sometimes with subulate scales around the margins; gynoecia terminal on thalli, stalks slightly purplish, 1‑‑3 cm with pale, long, fine, hairlike scales at apices, none at bases; carpocephala pale green, 4‑‑5 mm across, hemispheric, becoming umbonate with age, distinctly lobed with 3‑‑4(‑‑5) lobes directed horizontally outward; pseudoperianths conical, white with 12 or more segments, connate at apices. Sporophyte capsules yellowish; spores yellow, 100‑‑120 µm; elaters yellowish, 1‑‑2 spiral, 250‑‑300 µm.
Capsules mature Jan.--May. Soil of shaded banks in rather dry areas; Ariz. (Gila Co.), Calif., sw Oreg.; Mexico (Baja California Norte).
This is the only dioecious species in the flora. The female receptacles are large for the size of the plant and the pseudoperianths are directed outward horizontally rather than downward. The pale color of the carpocephala is in sharp contrast with the inrolled thalli covering the green upper surface exposing the dark purple underside.
7. Asterella lindenbergiana (Corda) Lindberg, Musc. Scand. 1. 1879
Fimbriaria lindenbergiana A. Corda in C. Nees von Esenbeck, Naturg. Eur. Leberm. 4: 283. 1838
Plants green, often pigmented with reddish‑purple blotches above, purplish‑red along the undulate, ascending margins and below; branching dichotomous, ventral intercalary branches infrequent. Thalli 10‑‑30 ´ 4‑‑6 mm; epidermis faintly areolate, cells 30 ´ 25 µm with thin walls and no trigones, oil cells few, scattered; air pores surrounded by 3‑‑4 tiers of 6‑‑8 scarcely differentiated cells; ventral scales large, purple with scattered oil cells; appendages 1‑‑2, white, lanceolate to acuminate. Sexual condition paroecious or autoecious, androecia posterior to gynoecial stalks or on separate branches, ovate, with variable number of papillae, or forming dorsal streaks of papillae; gynoecia terminal on main thalli; stalks purplish, 1.5‑‑2.5 cm with hairlike scales at bases and apices; carpocephala 3‑‑4 mm across, conical with low tubercules above and 3‑‑4 short lobes directed downward; pseudoperianths pleated, often purplish, of 12 or more segments with connate apices. Sporophyte capsules purple; spores deep purple, 80‑‑100 µm; elaters purple, 2‑spiral, 100‑‑150 µm.
Capsules mature July--Aug. Damp, mossy soil, frequently calcareous, arctic‑alpine; Alta., B.C.; Alaska, Colo., Mont., Oreg., Utah, Wash., Wyo.; Mexico; South America (Colombia); Europe.
The purple spores and elaters of this species are distinctive and when fruiting it can be readily separated from other species in the flora on that basis.
8. Asterella saccata (Wahlenberg) A. Evans, Contr. U.S. Nat Herb. 20: 276 1920
Marchantia saccata Wahlenberg, Ges. Nat. Freund. Berlin Mag. 5: 296 1811
Plants green above, purplish along margins and underneath, the thalli curl upward around apical margins exposing white scale appendages, forming a conspicuous apical tuft; branching dichotomous, ventral intercalary branches infrequent. Thalli 5‑‑10 ´ 2‑‑3 mm; epidermis smooth, cells 20 ´ 30 µm with slightly thickened walls and small trigones; air pores indistinct, surrounded by 1‑‑3 tiers of 5‑‑7 scarcely differentiated cells, oil cells few, scattered; ventral scales deep purple, long tapered, with scattered oil cells; appendages 1‑‑2, white, long tapered lanceolate to acuminate, as long or longer than scales, curling up around the anterior thalli margins, forming conspicuous white clusters at apices. Sexual condition paroecious, occasionally autoecious; androecia form ill‑defined dorsal streaks of papillae at posterior bases of gynoecial stalks or on nearby branches; gynoecia terminal on main thalli, stalks 1‑‑2 cm, purplish with cluster of white hairlike scales at bases and none at apices; carpocephala 2‑‑3 mm across, ovate, at least 1‑1/2 times taller than wide with 3‑‑4 lobes directed downward; pseudoperianths conical, of 6‑‑8 white segments, connate at apices. Sporophyte capsules yellowish; spores yellow to pale brown, 80‑‑90 µm; elaters yellowish, 1‑‑3 spiral, 150‑‑200 µm.
Capsules mature May. Soil in rock crevices, usually calcareous in arctic‑alpine areas; Greenland; Alta.; Alaska, Minn., Mont., Wash.; Europe; Asia.
The white scale appendages exposed at thalli apices and along upturned margins are distinctive. These scale clusters have caused confusion with Mannia fragans, which has a similar apical cluster. Unconfirmed reports from areas south of this species' range may represent M. fragans, which also lacks a pseudoperianth and has brown, not yellow spores.
Grolle, R. 1975. Miscellanea hepaticologica (141‑150) J. Bryol. 8: 483‑-492.
Schuster, R. M. 1985. Some new taxa of Hepaticae. Phytologia 57: 410.
Schuster, R. M. 1992. The Hepaticae and Anthocerotae of North America. Chicago.
Stotler, R. and B. Crandall‑Stotler. 1977. A checklist of the liverworts and hornworts of North America. Bryologist 80: 405-‑428.
Sullivant, W. S. 1856. The musci and hepaticae of the United States east of the Mississippi River. In: A. Gray, Gray's Manual of Botany Ed. 2, pp. 607‑-737, pls 1-‑8.
Underwood, L. M. 1884. Descriptive Catalogue of the North American hepaticae, North of Mexico. Bull. Illinois State Lab. Nat. Hist. 2: 1‑133.