American Species of Marchantia. 291 



Grimaldia peruviana Nees & Mont. ; Montagne, Fl. Boliv. in 



D'Orbigny, Voy. dans I'Amer. Merid. 7^ : 53. 1839. 

 Marchantia peruviana Nees ; G. L. & N, Syn. Hep. 538. 1847. 

 Marchantia Dillenii Lindb. Krit. Gransk. Hist. Muse. 47. 1883. 



Thallus pale or yellowish green, sometimes more or less 

 glaucous, usually tinged with purple or brownish on the lower 

 surface, usually 4-7 mm. wide and 2-3 cm. long, dichotomous, 

 the successive forks averaging about i cm. apart, texture varying 

 from firm and often leathery to delicate, margin entire ; epidermis 

 composed of cells with slightly thickened walls, often in two 

 layers, mostly 30-601U, long (averaging about 4.0fx) and i5-30/x 

 wide (averaging about 22/x), papillae absent, slime cells often 

 present, averaging about Gojx in diameter ; pores variable in size, 

 usually (with their surrounding cells) measuring 100-170/1, in 

 length and 80-130/x in width but sometimes considerably smaller, 

 usually surrounded by seven rows of cells (four in the upper 

 series and three in the lower), more rarely by six, eight or even 

 nine rows, the two upper rows of the upper series and the two 

 lower rows of the lower series composed of four to six cells 

 apiece, the third row of each series usually of twice as many, 

 and the fourth row of the upper series usually of a much larger 

 number, sometimes of as many as eighteen, inner opening four- 

 to six-sided with the sides straight or more or less concave, cell- 

 walls mostly smooth throughout ; air-chambers of medium 

 height, isodiametric or somewhat elongated, their boundaries 

 usually distinct but sometimes obscure when viewed through 

 the epidermis, present everywhere, cells of partition walls some- 

 times including slime cells, rows of photosynthetic cells usually 

 three or four cells long; compact ventral tissue mostly twenty 

 to twenty-five cells thick in the median portion, the walls some- 

 times pigmented, more or less thickened and showing distinct 

 pits, sclerotic cells usually distinct, scattered, mostly twenty to 

 fifty in a cross-section, usually abundant in both median portion 

 and wings, slime cells usually present, scattered, tending to be 

 more abundant in the wings, rarely more than six or eight in a 

 cross-section; ventral scales in two distinct rows, the laminar 

 scales alternating with the median scales and not much nearer 

 the margin; appendages of the median scales very variable, 

 lanceolate to broadly ovate, when well developed mostly 0.45- 

 0.65 mm. long and 0.3-0.4 mm. wide but sometimes considerably 

 smaller, apex acuminate, acute or apiculate, margin entire or 

 variously and irregularly toothed, the teeth rarely numerous and 

 often restricted to the basal portion, cells of about the same size 

 throughout or showing a slight and gradual decrease in size 

 toward the margin, median cells usually longer than broad, 

 mostly 60-90JU, long and 25-40/i wide, marginal cells mostly 30-70)1* 



