American Species of Marchantia. 241 



2. Marchantia plicata Nees & Mont. 



Marchantia ( ?) plicata Nees & Mont. ; Montagne, Ann. Sci. Nat. 



Bot. II. 9 : 43. 1838. 

 Marchantia lamellosa Hampe & Gottsche-; G. L. & N. Syn. Hep. 



527. 1846. 

 Marchantia vtdcanica Spruce, Trans. Bot. Soc. Edinburgh 



15 : 559. 1885 (as synonym). 



Thallus green, not glaucous, often more or less pigmented with 

 purple on the lower surface, usually 1-1.5 cm. wide, often 6-8 cm. 

 long or even more, occasionally dichotomous, the successive forks 

 usually about 2 cm. apart, texture delicate, margin entire ;• epi- 

 dermis composed of thin-walled cells, averaging about 20/x in 

 length and 13/i in width, papillae absent; pores (with their sur- 

 rounding cells) mostly 65-80/i, long and 50-60/A wide, gradually 

 decreasing in size toward the margin, the smallest measuring 

 about 50 X 40/X, surrounded by three or (usually) four rows of 

 cells (two rows being in the lower series), each row being usually 

 composed of four cells, inner opening mostly four-sided, with 

 slightly convex to distinctly concave sides, somewhat roughened 

 by a resinous deposit ; air-chambers low, isodiametric or some- 

 what elongated, their boundaries very indistinct when viewed 

 through the epidermis, everywhere present (except close to the 

 margin), rows of photosynthetic cells usually less than three 

 cells long; compact ventral tissue mostly twenty to twenty-five 

 cells thick in the median portion, destitute of slime cells and 

 sclerotic cells, the cell-walls slightly thickened and with distinct 

 pits ; ventral scales in four to six rows on each side of the thallus, 

 median and marginal scales in distinct rows, laminar scales in 

 two to four indistinct rows, scales often pigmented with purple, 

 marginal scales more or less imbricated and usually projecting 

 beyond the margin ; appendages of median scales orbicular-ovate 

 to orbicular, mostly 0.65-0.9 mm. long and 0.65-0.8 mm. wide, 

 somewhat narrowed toward the rounded and sometimes apiculate 

 apex, margin minutely and irregularly denticulate or crenulate, 

 a tooth sometimes consisting of an entire cell borne on a slightly 

 projecting stalk cell, cells rapidly decreasing in size toward the 

 margin, median cells mostly 70-90/x in length and 40-60/x in 

 width, marginal cells only 25-5O1U. in length and 12-20/x in width, 

 cells containing oil-bodies 15-30/* in diameter, usually about ten 

 on each appendage, restricted to submarginal portions : male 

 receptacle borne on a stalk 2-3 cm. long, with two rhizoid-fur- 

 rows, destitute of dorsal air-chambers, the disc mostly 1-1.2 cm. 

 broad (when well developed), deeply lobed, the lobes or rays 

 mostly eight (sometimes nine or ten), the two basal rays usually 

 separated by a wider sinus than the others, 2-4 mm. long, rounded 

 at the apex and with thin wavy margins, covered ventrally with 



