M ar chant iacecz. 
161 
however, several specimens of 5. alpina with involucres each con¬ 
taining from two to four archegonia; in some cases two sporogonia 
had developed in an involucre, and frequently the stalk had two 
furrows containing the rhizoids, which spring from the underside of 
the receptacle between the involucres. 
Apart from the constant occurrence of two rhizoid-furrows in 
the stalk, Peltolepis agrees closely with Sauteria in the structure of 
the carpocephalum. In P.graudis, which Leitgeb and other writers 
describe as resembling Clevea and Sauteria in having a single 
archegonium in each involucre, numerous cases were observed in the 
writer’s Swiss specimens, in which each involucre had two, three, 
four, and even five archegonia in an involucre, though only one 
sporogonium was produced in the plants examined. Hence in both 
Sauteria and Peltolepis the carpocephalum is of the “ Composite ” 
type. 
The Astroporae form an interesting series, marked off from the 
other Marchantiaceae by the structure of the thallus and by the 
scattered and simple ventral scales; while they are still more 
sharply distinguished from the Operculatse by the structure of the 
capsule-wall. 
II.—Operculatae. 
Leitgeb named this group from the mode of dehiscence of the 
capsule in the genera known to him. The capsule-wall has an 
apical lid which is either thrown off entire or breaks up irregularly, 
and the lower part of the dehisced capsule remains as an urn, 
usually with toothed margin. The cells forming the capsule-wall 
are devoid of special fibrous thickenings, though in the upper half 
of the capsule the cells often have their radial walls slightly 
thickened at the corners. From the Astroporse the group is further 
distinguished by several other characters: the ventral scales are in 
two rows and have well-defined apical appendages (sometimes two 
or three to each scale); the pores on the thallus are surrounded by 
several concentric rings of cells ; the pores on the sexual receptacles 
are barrel-shaped. It is more difficult to separate the Operculatae 
from the Composite, for in all the genera, except Plagiochasma and 
and the incompletely known new genus Massalongoa, more than one 
archegonium may be developed in each involucre of the carpo¬ 
cephalum, and among the Composite there are genera which 
resemble the Operculatae in thallus structure ( Ducegia ) and in the 
absence of fibres from the capsule-wall ( Lunularia ). Still, the 
group may be regarded as forming an independent series, showing 
