592 Evans: REPORT ON THE HEPATICAE OF ALASKA 
relatively broader, the ratio of width to length being 0.9 instead 
of only 0.7-0.75 as in P. alaskana. The greater relative breadth 
is due largely to a strong dilation at the postical base. The 
marginal teeth in the two Asian species are much like those in 
P. alaskana but usually number from thirty to forty. In P. rent- 
tens the decurrent portion at the antical base is entire, but in 
P. trapezoidea it is distinctly dentate and the species is further 
remarkable on account of the short and narrow lamina or para- 
phyllium which runs parallel with the decurrent portion and is 
situated in its near vicinity. In P. renitens the deflexed and 
postically secund habit is particularly well marked. The cells 
in both Asian species are somewhat larger than in P. alaskana, 
those in the apical portion measuring about 20m in diameter 
those in the middle about 30X20 yw, and the elongated basal cells 
about 60 X20 u; the trigones, especially in P. trapezoidea, are more ~ 
clearly defined than in P. alaskana, coalescence being less prev- 
alent. 
To a considerable extent the section Denticulatae of Schiffner 
corresponds with the section Heteromallae of Spruce.* Of this 
group, to which Spruce refers thirteen South American species, 
the following may be profitably compared with P. alaskana: 
P. pachyloma Tayl.,} P. oxyphylla Spruce,t and P. fragilis Tayl.,§ 
all of Ecuador. These three species show most of the characters 
emphasized under P. alaskana, although the elongation of the: 
basal cells is not apparent in either P. pachyloma or P. oxyphylla, 
nor is the deflexed and postically secund habit always marked. 
In P. pachyloma the leaves are almost as broad as long and 
measure about 2.2 cm. in length in the specimens studied by the 
writer, although Spruce gives a length of 2.75 mm. and Stephani 
alengthof 3mm. The postical base is strongly dilated, the antical 
margin is entire except near the apex, while the postical margin 
and the apical region are sharply spinose-dentate. The total 
number of teeth being about thirty. The species is peculiar in 
the brownish pigmentation of the teeth, ia the strongly thickened 
* Hep. Amaz. et And. 458. 1885. 
6. 
ft Hep. Amaz. et And. 480. 1885. 
