American Species of Marchantia. 265 



a horizontal position. Although the normal number of rays in 

 M. paleacea is nine, just as in M. polymorpha, deviations from 

 this number sometimes occur, a reduced number being associated 

 with poor development. 



According to Prescher scattered slime cells of small size are 

 present in the walls of the cupules of M. paleacea but are lack- 

 ing altogether in the thallus and in the female receptacles. 

 Although the thallus sometimes agrees with his account it does 

 not always do so. Cases have been observed in which slime 

 cells formed a rather conspicuous feature of the ventral tissue 

 of the wings, an occasional cell of this character being present 

 even in the thickened median region. In other cases, the slime' 

 cells were less abundant. In the male receptacles, which Prescher 

 did not examine, slime cells are fairly numerous. It is evident 

 from these observations that the presence or absence of slime 

 cells can not be utilized in distinguishing M. paleacea. 



5. Marchantia breviloba sp. nov. 



Thallus pale green, more or less glaucous, sometimes a little 

 pigmented with purple, especially near the margin and on the 

 lower surface, mostly 0.5-0.8 cm. wide and 2-5 cm. long, repeat- 

 edly dichotomous, the successive forks usually 1-2 cm. apart, 

 texture firm but not leathery, margin entire ; epidermis composed 

 of cells with somewhat thickened walls, sometimes in two layers 

 mostly 45-90/i, long (averaging about 65/*) and 20-40/* wide 

 (averaging about 28/x), papillae absent; pores (with their sur- 

 rounding cells) mostly 125-150^1 long and 100-120/1 wide, sur- 

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

 series or sometimes four in the outer series), innermost row 

 of upper series usually composed of four cells, second row of 

 four to eight cells and third row of eight or more cells, each row 

 of lower series usually composed of four cells, inner opening 

 usually four-sided (sometimes three-, five-, or six-sided), the 

 sides being concave and forming acute angles with one another, 

 bounding cells of pore more or less roughened with a resinous 

 deposit ; air-chambers usually high, more or less elongated, their 

 outlines very indistinct when viewed through the epidermis, 

 present everywhere, rows of photosynthetic cells often four or 

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

 five cells thick in the median portion, the walls sometimes pig- 

 mented, more or less thickened and showing distinct pits, scle- 

 rotic cells distinct, scattered, about forty in a cross-section, 

 largely confined to median region, sometimes as much as 0.7 mm. 

 in length, slime cells about o.i mm. in diameter, usually con- 



Tpans. Conn. Acad., Vol. XXI 18 19^7 



