American Species of Marchantia. 2^7 



8. Marchantia Bescherellei Steph. 

 Marchantia Bescherellei Steph. Rev. Bryol. 15 : 86. 1888. 



Thallus dull green, not glaucous, slightly or not at all pig- 

 mented with purple, mostly 5-7 mm. wide and 2-3 cm. long, 



I dichotomous, the forks 1-1.5 cm. apart, texture very delicate, 

 margin entire, sometimes vaguely and irregularly plicate; epi- 

 dermis composed of cells with very thin walls, in a single layer, 

 mostly 40-70/X long (averaging about 50/*) and 20-35/x wide 

 (averaging about 25^*), papillae absent; pores (with their sur- 



\ rounding cells) mostly i6o-200/>t long and i20-i6o/x wide, 



I surrounded usually by seven or eight rows of cells, three or four 

 in the upper series and four in the lower series, the two lower 



' rows of the upper series usually composed of ten to twelve or 

 even more cells apiece, the other rows of five or six cells, rarely 

 of only four cells apiece, inner opening usually five- or six- 

 sided, rarely only four-sided, with the sides strongly concave, 

 resinous deposit slight; air-chambers low, somewhat elongated, 

 their boundaries indistinct when viewed through the epidermis, 

 present everywhere except close to the margin, rows of photo- 

 synthetic cells usually two or three cells long; compact ventral 

 tissue mostly twelve to fifteen cells thick in the median portion, 

 abruptly thinning out in the wings, the walls somewhat pig- 

 mented, slightly or not at all thickened, sclerotic cells scattered, 

 sparingly developed, slime cells lacking; ventral scales in two 

 rows, the laminar scales alternating with the median scales and 

 not much nearer the margin; appendages of the median scales 

 ovate, when well developed mostly 0.5-0.6 mm. long and 0.35- 

 0.45 mm. wide but often smaller, apex acute, margin sparingly 

 and irregularly dentate, the teeth in the basal portion often 

 larger and sharper and sometimes lobe-like, cells showing a 

 gradual and slight decrease in size toward the margin, median 

 cells usually longer than broad, mostly 50-80/x long and 30-40/^ 

 wide, marginal cells mostly 30-50/x long and 15-25/A wide, irregu- 

 lar but usually perpendicular or nearly so to the margin, cells 

 containing oil-bodies lacking: male receptacle borne on a stalk 

 about I cm. long (iji the only example studied), with two rhizoid- 

 furrows and (apparently) with a single broad dorsal band of 

 air-chambers, the disc 7 mm. broad, with four short and rounded 

 lobes or rays with thin margins, basal sinus more than 180 degrees, 

 the other sinuses narrow, ventral scales apparently in two rows : 

 female receptacle borne on a stalk about 2 cm. long (in the only 

 example studied), with two rhizoid-furrows and dorsal air- 

 chambers apparently in two distinct bands, the disc about 7 mm. 

 wide, with five short and rounded lobes or rays, upper surface of 

 receptacle plane, basal sinus a straight line or nearly so ; involucre 

 delicate, closely and irregularly dentate, some of the teeth three 

 or four cells long and two to four cells wide at the base, other 



