American Species of Marchantia. 233 



with purple, the marginal scales close together though scarcely 

 imbricated, usually projecting beyond the margin; 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, sometimes 

 apiculate, margin usually minutely and irregularly denticulate, 

 sometimes (in hygrophilous forms) tending to be crenulate, cells 

 showing a gradual decrease in size toward the margin, median 

 cells subisodiametric, mostly 35-40/^1 in diameter, marginal cells 

 mostly 20-25 ju, long and 14-16/A wide, sometimes smaller (io-i6fix 

 lO/x), cells containing oil-bodies about 20/x in diameter, usually 

 from five to ten on each appendage, restricted to submarginal 

 (and, rarely, marginal) portions: male receptacle borne on a 

 stalk 1-3 cm. long with two rhizoid-furrows, destitute of dorsal 

 air-chambers, the disc mostly 0.7-1 cm. broad, shortly lobed or 

 merely crenate, the lobes or rays mostly eight (rarely nine or ten), 

 2 mm. long or less, rounded at the apex with thin wavy mar- 

 gins, covered ventrally with densely imbricated scales in several 

 rows : female receptacle borne on a stalk 2-7 cm. long, with two 

 rhizoid-furrows and a single broad dorsal band of air-chambers, 

 the disc mostly 0.8-1.3 cm. broad, deeply lobed, the lobes or rays 

 spreading at maturity, mostly nine (sometimes ten or eleven), 

 3-5 mm. long, separated by subequal sinuses, terete, covered over 

 with epidermal papillae; involucre deeply and irregularly lobed, 

 the lobes long-acuminate and ciliate on the margins: spores 

 yellow, I2-I5ju in diameter, fiearly smooth; elaters 3-5/* wide, 

 bispiral: cupules deeply lobed, the lobes acute to acuminate, 

 usually dentate to short-spinose on the sides, outer surface with 

 epidermal papillae. (Figs, i, 2.) 



Throughout the greater part of Europe and in the northern 

 parts of Asia and North America M. polymorpha is the only 

 representative of the genus and is exceedingly abundant. It 

 grows in swamps and bogs, on rocks and walls near the ground, 

 on banks and the sides of ditches, in gardens and greenhouses, 

 and on the earth in fields and woods. It is perhaps most luxuriant 

 in bogs and on steep rocky hillsides where a liberal supply of 

 water is available. In the woods it is especially likely to occur 

 where a fire has left a supply of charcoal behind. Toward the 

 south other species of Marchantia make their appearance and 

 M. polymorpha becomes less abundant. In many places it pre- 

 sents the appearance of being an introduced plant. 



A search through the literature shows that the occurrence of M. 

 polymorpha south of the equator has been doubted or denied 

 by certain authors. Hooker,^ for example, about fifty years ago, 



' See Handb. New Zealand Fl. 545. ^^^7- 



Trans. Conn. Acad., Vol. XXI 16 1917 



