M arcliantiacea. 
167 
Britain, the carpocephalum, which has well-developed air-chambers, 
is conical or hemispherical when young, with four to seven thick 
lobes, the margins of which form bivalved involucres, each with a 
single archegonium (sometimes two archegonia). When the capsules 
ripen, the lobes spread upwards and outwards, so that the receptacle 
becomes nearly horizontal. The apical portion of the capsule-wall, 
which has a well-developed cap (Fig. 23), falls away in fragments 
when the capsule opens. The series of figures given here will serve 
to illustrate the structure of this plant, which forms a good average 
type of the Operculatae. 
Grimaldia (Fig. 19, III.) and Neesiella (Fig. 19, IV.) are closely 
allied to Reboulia, but the upper portion of the capsule-wall becomes 
detached in a single piece, forming a well-defined lid. The limit of the 
latter, and the dehiscence of the capsule, are in these two genera 
determined by an annulus consisting of small cells, which does not 
occur in any of the other Operculatae. Moreover, in these genera the 
sinuses from which spring the rhizoids that run into the furrow of 
the carpocephalum stalk bulge slightly outwards and are visible as 
short lobes on the outer surface of the carpocephalum, alternating 
with the bell-shaped involucres ; these lobes correspond with the long 
hollow rays seen in Marchantia. In both genera, also, the writer 
has found that the involucres frequently contain two ( Grimaldia 
fragans, G. dichotoma) or as many as four ( Neesiella rupestris) 
archegonia. The archegonia have usually been described as occurring 
singly in the involucres, though Leitgeb noted the occurrence of two 
archegonia in one case in Neesiella. In one specimen of Grimaldia 
fragans the writer found two sporogonia in an involucre, but in 
several cases every involucre examined had two archegonia. 
In Cryptomitrinm, Abrams (1) has shown that each involucre 
contains a group of archegonia (usually five) which show centrifugal 
development exactly as in the Composite. Moreover, Stephani 
(61) states that the stalk often has two furrows, and we have here 
again a typical “ Composite ” carpocephalum, with five or six 
growing-points from which the archegonia are developed. 
The large genus Fimbriaria differs from the other Operculatae 
in having a special envelope (perianth) around each archegonium, 
arising from the tissue inside the involucre ; in this respect the 
genus resembles the highest types of the Marchantiaceae ( Preissia 
and Marchantia). The recently discovered Himalayan genus Massa- 
lonwa is said by Stephani (62) to stand near Fimbriaria , but it has 
no perianth. The perianth of Fimbriaria is a striking and beautiful 
