246 Alexander W. Evans, 



The crowded marginal scales, however, visible from above, seem 

 to be a constant feature, although these scales may not be any- 

 more conspicuous than in M. polymorpha. The appendages of 

 the ventral scales, as in other species, yield some of the most 

 important characters (Fig. 3). The small marginal cells are 

 exceedingly irregular, forming various angles with the periphery 

 of the appendage and often projecting in the form of blunt teeth. 

 Frequently a projecting cell will be borne on a broader basal cell, 

 a two-celled tooth of a peculiar type being thus produced. 

 Usually the difference in size between the marginal cells and the 

 interior cells is very marked, but the difference is less when the 

 appendages are poorly developed (Fig. 3, A). The apices of the 

 appendages are especially variable. In some cases a distinct 

 apical tooth two cells long is present, making the appendage 

 apiculate (Fig. 3, F) ; in other cases the apical tooth is hardly 

 distinguishable from the neighboring teeth (Fig. 3, G) ; in still 

 other cases there is no indication whatever of an apical tooth 

 (Fig. 3, H, I). 



When the appendages are compared with those of M. poly- 

 morpha they are found to have many features in common. In 

 both species they are similar in form and show a decrease in the 

 size of the cells in passing from the middle to the margin; in 

 both species the apex is variable and the margin is normally 

 denticulate. In M. plicata, however, the cells are larger and the 

 decrease in size more abrupt, the denticulation tends to be more 

 pronounced, owing largely to the frequency of two-celled teeth, 

 and the marginal cells tend to be more irregular. Although these 

 differences are of a comparative nature and subject to variation, 

 they will usually be found serviceable in separating the species. 



3. Marchantia Berteroana Lehm. & Lindenb. 



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

 6:21. 1834. 



Marchantia tabularis Nees, Naturg. Europ. Leberm. 4: 71 (foot- 

 note). 1838. 



Marchantia cephaloscypha Steph. Hedwigia 22 : 51. 1883. 



Thallus green or bluish green, sometimes glaucous, often more 

 or less pigmented with purple or brownish near the margin and 

 on the lower surface, usually 1-1.5 cm. wide and 6-8 cm. long, 



