American Species of Marchantia. 247 



variously dichotomous, the successive forks sometimes 2-3 cm. 

 apart but often closer together, texture usually tough and 

 leathery, margin entire or minutely and irregularly denticulate 

 or crenulate, more or less plicate ; epidermis composed of cells 

 with thin or slightly thickened walls, mostly 20-60|U, long (aver- 

 aging about 32/x) and 16-24/x wide (averaging about 19/*), 

 papillae absent; pores (with their surrounding cells) mostly 

 60-80/A long and 50-60/x, wide, surrounded usually by six rows 

 of cells (three in each series), each row being usually composed 

 of four cells, inner opening cruciate, the bounding cells commonly 

 four (rarely three or five), slightly roughened; air-chambers of 

 medium height, usually a little longer than broad, their boundaries 

 indistinct when viewed through the epidermis, present every- 

 where, rows of photosynthetic cells usually three or four cells 

 long ; compact ventral tissue about twenty-five cells thick in the 

 median portion, destitute of slime cells and sclerotic cells, usually 

 thin-walled and with indistinct pits ; ventral scales in two rows, 

 median and laminar, no marginal scales being present, scarcely 

 imbricated, pale or brownish ; appendages of median scales 

 orbicular-ovate to broadly orbicular, usually somewhat narrowed 

 toward the rounded apex, mostly 0.6-1 mm. in length and about 

 the same in width, margin minutely and often regularly crenulate 

 or denticulate from projecting cells, cells showing an abrupt 

 decrease in size toward the margin, median cells mostly 60-85/x 

 long and 20-4O/L1 wide, marginal cells (in one, two, or three 

 rows) mostly I2-20|U, long and 8-i2;u, wide, cells containing oil- 

 bodies about 20/A in diameter, about five on each appendage, 

 restricted to svibmarginal portions : male receptacle borne on a 

 stalk 1-5 cm. long with two rhizoid-furrows, destitute of dorsal 

 air-chambers, the disc about i cm. in diameter, more or less 

 deeply lobed when well developed, the lobes or rays mostly eight, 

 usually 2-3 mm. long, rounded at the apex and with thin wavy 

 margins, covered ventrally (except in the marginal portions) with 

 imbricated scales in several rows, sinuses usually subequal in 

 width : female receptacle borne on a stalk mostly 3-8 cm. in 

 length, with two rhizoid-furrows and a broad dorsal band of air- 

 chambers, the disc mostly 0.8-1 cm. broad, deeply lobed, the 

 lobes or rays spreading at maturity, mostly nine, 2-3 mm. long, 

 separated by subequal sinuses, terete, rounded, destitute of epi- 

 dermal papillae; involucre much as in M. polymorpJia: spores 

 brownish yellow, mostly 8-10^ in diameter, smooth; elaters about 

 5ju, wide, bispiral : cupules deeply lobed, the lobes as in M. poly- 

 morpJia, outer surface with epidermal papillae. (Fig. 5.) 



A widely distributed species, restricted (according to our 

 present knowledge) to the Southern Hemisphere. The follow- 

 ing South American specimens have been examined : 



