American Species of Marchantia. 253 



Section II. Chlamidium 

 4. AIarchantia paleacea Bertol. 



Marchantia paleacea Bertol. Opus. Sci. Bologna i : 242. 1817. 

 Marchantia papillafa /? italica Raddi, Mem. Soc, Ital. Modena 



19:44. 1823. 

 Fimhriaria paleacea Corda; Opiz, Beitr. zur Naturg. 648. 1828. 

 Fegatella Michelii Corda, /. c. 649. 1828 (according to Nees von 



Esenbeck). 

 Marchantia nepalensis Lehm. & Lindenb. ; Lehmann, Pug. Plant 



4: 10. 1832. 

 Marchantia nitida Lehm. & Lindenb. /. c. 11. 1832. 

 Marchantia squamosa Raddi; Lehm. & Lindenb. /. c. 12. 1832 



(as to the East Indian plant). 

 Marchantia tholophora Bisch. Nova Acta Acad. Leop.-Carol. 



17:989. 1835. 

 Marchantia calcarata Steph. Bull. Herb. Boissier 5 : 98. 1897. 

 Marchantia planipora Steph. /. c. 98. 1897. 



Thallus pale green, often glaucous, sometimes more or less 

 pigmented with purple, especially near the margin and on the 

 lower surface, usually 0.5-0.8 cm. wide and 2-4 cm. long, 

 repeatedly dichotomous, the successive forks usually i cm. or 

 less apart; texture firm but scarcely leathery, margin entire; 

 epidermis composed of cells with more or less thickened walls, 

 sometimes in two layers, mostly 35-70/x long (averaging about 

 43)Li) and 20-40/^ wide (averaging about 30ju,), papillae absent; 

 pores (with their surrounding cells) mostly 70-90/^ long and 

 65-8511!, wide, sometimes measuring as much as 140 x lOOjx, sur- 

 rounded usually by six (or seven) rows of cells (three in the 

 upper and three or four in the lower series), each row being 

 usually composed of four cells or the innermost row of the upper 

 series of from four to eight cells, inner opening cruciate, the 

 bounding cells smooth ; air-chambers usually high, isodiametric 

 or slightly elongated, their boundaries indistinct when viewed 

 through the epidermis, present everywhere, rows of photosyn- 

 thetic cells often six or seven cells long but sometimes shorter; 

 compact ventral tissue mostly twenty to thirty cells thick in the 

 median portion, the walls sometimes pigmented, more or less 

 thickened and showing distinct pits, sclerotic cells usually dis- 

 tinct, scattered, ten to twenty in a cross-section of thallus, more 

 abundant in median region but not confined to this, slime-cells 

 sometimes lacking, sometimes more or less abundant, especially 

 toward the margin; ventral scales in two distinct rows, the 

 laminar scales alternating with the median and only a little nearer 



