Common Liverwort

Marchantia polymorpha L. Sp. PI. 1137. 1753
Marchantia stellata Scop. Fl. Cam. ed. 2. 353. 1772. Marchantia umhellata Scop. Fl. Carn. ed. 2. 354. 1772. Marchantia polymorpha domestica Wahlenb. Fl. Lapp. 397. 1812. Marchantia latifolia S. F. Gray, Nat. Arr. Brit. PI. 1: 682. 1821. Marchantia minor S. F. Gray, Nat. Arr. Brit. PI. 1: 682. 1821. Marchantia macrocephala Corda; Sturm, Deuts. Fl. Jungerm. 63. 1832. Marchantia vittata Raddi, Mem. Soc. Ital. Modena 20; 45. 1829. Marchantia polymorpha communis Nees, Naturg. Em". Leberm. 4: 65. 1838. Marchantia polymorpha alpestris Nees, Naturg. Bur. Leberm. 4: 70. 1838. Marchantia Syckorae Corda; Nees, Naturg. Eur. I^berm. 4: 97. 1838. Marchantia oregonensis Stephani; Roll, Bot. Centr. 45: 203. 1891. Marchantia polymorpha mamillata Hagen; SchifFn, Lotos 49: 93. 1901.
Thallus pale-green to dark-green, sometimes with a brownish median band, often purplish beneath, mostly ^6 cm. long and about 1 cm. wide, texture delicate or firm but never leathery; ■epidermal cells averaging about 29 X 16 /x; surface-papillae sometimes present near margin of thallus; pores usually bounded by 4 circles of cells with 4 cells in each circle, those of the innermost circle with rounded papillae sometimes almost closing the opening; ventral tissue ■destitute of sclerotic cells and slime-cells; ventral scales in 6 more or less distinct rows, the -marginal scales usually projecting; appendages of median scales broadly orbicular, mostly 0.5-0.75 mm. long and 0.6-0.8 mm. wide, rounded to very bluntly pointed, the margin minutely ^nd irregularly denticulate or crenulate. Male receptacle borne on a stalk 1-3 cm. long with 2 rhizoid-fiUTows, destitute of green tissue, mostly 0.7-1 cm. broad, shortly lobed or merely crenate, the lobes mostly 8, subsymmetrically spaced; female receptacle borne on a stalk 2-7 cm. long, with two rhizoid-furrows and a single broad band of green tissue, mostly 0.8-1,3 •cm.wide, deeply rayed, the rays mostly 9, Z-5 mm. long, separated by subequal sinuses, terete, with numerous surface-papillae; involucre deeply and irregularly lobed, the lobes long-acuminate and with ciliate margins; spores yellow, 12-15 m in diameter, nearly smooth; elaters 3-5 ,/t wide. Cupules deeply lobed, the lobes acute to acuminate, dentate to short -spinose, the outer surface with papillae.
Type i;ocality: Europe.
Distribution: Greenland to Alaska, and southward throughout Canada and the United States; Mexico, Central America, Bermuda, and the West Indies; also in Europe, Asia, South America, and various antarctic islands ; on banks and earth in woods, fields, and gardens ; also in swamps and bogs ;
■sometimes apparently introduced.
Ii^LUSTRATiONs : Micheli, Nov. PI. Gen. pi, IJ, 1-3, 5. 6; Dill. Hist. Muse. pi. 76, 77, f. 7; Nouv. Ann. Mus. 1: pi. 5-7; Sturm, Deuts. Fl. Jungerm. pi. 17; Kny, Bot. Wandtaf. pi. 84-90; Pearson, -Hep. Brit. Isles pi, 208; Rab. Krypt.-Fl. 6:/. 185-187; Atti 1st. Veneto 75: pi. 1; Trans. Conn.
Acad. 21' f. 1 2.