268 Alexander W. Evans, 



female and gemmiparous material. Two, bearing the numbers 

 5 and 6, are labeled "Marchantia conica" ; the other two bear 

 no name. No. 175, collected by the writer, may be designated 

 the type. 



The thallus of M. breviloha bears a strong resemblance to 

 that of M. paleacea, being of about the same size and similarly 

 subject to pigmentation. The ventral scales and the appendages 

 of the median scales in these two species likewise have certain 

 features in common. The arrangement of the scales, for exam- 

 ple, is very similar and the appendages agree in form, in the grad- 

 ual decrease in the size of the cells in passing toward the margin, 

 and in some of the peculiarities of the margin itself. Even the 

 pores look a good deal alike when examined through a lens. A 

 detailed examination, however, quickly brings out points of dif- 

 ference. In M. breviloba the pores are not of the cruciate type, 

 the inner opening (so far as observed) being surrounded by evenly 

 bulging cells and thus usually exhibiting a four-sided outline 

 with concave sides and narrow angles ; in M. paleacea the pores 

 are distinctly cruciate. In M. breviloba the cells of the appen- 

 dages are markedly larger than in M. paleacea and oil-containing 

 cells seem to be constantly absent; in M. paleacea oil-contain- 

 ing cells can often be detected. In M. breviloba slime cells seem 

 always to be numerous and conspicuous; in M. paleacea they 

 are less frequent and may be absent altogether: this last dif- 

 ference, unfortunately, is one to be used with caution. 



The differential characters yielded by the receptacles and 

 cupules, in separating M. breviloba from M. paleacea, are even 

 more marked than those derived from the thallus. In M. brevi- 

 loba the male receptacle is borne on a long stalk with a distinct 

 band of air-chambers and usually with four rhizoid-furrows; 

 and the disc is unsymmetrically divided into six or seven 

 elongated lobes, the basal sinus being much broader than the 

 others and often approximating a straight Hne. In M. paleacea 

 the male receptacle is borne on a very short stalk without air- 

 chambers and with only two rhizoid-furrows; while the disc is 

 very shortly and apparently radially divided into eight (or more) 

 often indistinct lobes, the basal sinus being of about the same 

 width as the others. 



In M. breviloba the stalk of the female receptacle shows four 

 rhizoid-furrows, and the disc is very shortly lobed, the lobes 



