104 
Cavers. — On the Structure and 
that normally occur may be suppressed, so that the receptacle may 
present only six or seven growing-points. The dorsal segments of 
each growing-point give rise at first to sterile tissue, in which air- 
chambers are formed in regular acropetal succession (PL VII, Fig. 46), 
whilst the ventral segments give rise to tuberculate rhizoids and ventral 
scales. Each of the latter consists simply of a club-shaped mucilage-hair 
terminating a short row of cells ; sometimes the cells below the club- 
shaped hair undergo longitudinal divisions, giving rise to two or three rows 
of cells. Whilst the branching has been taking place the whole receptacle 
has become hemispherical in form. The tissue of the receptacle grows 
much more rapidly in all directions than does the tissue which lies below 
and behind it and which gives rise to the receptacle-stalk, so that around 
the insertion of the stalk there is formed a deep but narrow annular 
groove. This is continuous in front with the rhizoid-bearing groove on 
the anterior face of the stalk, which in its turn becomes confluent with the 
ventral furrow of the thallus. In addition to tuberculate rhizoids, this 
groove bears two longitudinal rows of scales, which are smaller and simpler 
in structure as they are traced upwards, every possible transition being 
found between the ordinary ventral scales of the thallus, with their coloured 
discoid appendages, and the greatly reduced scales already described as 
being formed behind each of the growing-points of the receptacle. Each 
growing-point gives rise to a single archegonium. The first archegonium 
invariably arises on the hinder margin of the receptacle, and it is closely 
followed by the appearance of the second and third at the sides of the 
receptacle, the latest-formed one being nearest to the front of the re- 
ceptacle. Ultimately we find from six to nine archegonia in all, standing 
singly on the margin of the receptacle at approximately equal distances 
from each other. These early stages appear to be passed through 
very rapidly, and the archegonia are frequently found to be all in nearly 
the same stage of development, though the anterior ones are invariably 
less advanced than those occupying the hinder portion of the receptacle. 
Their development is obviously not simultaneous in any case, though it 
may sometimes be nearly so. 
On comparing the carpocephalum of Fegatella with that of M archantia 
polymorpha , the organization of which was long ago worked out correctly 
by Mirbel (1835), it will be seen that the only points of essential difference 
are (1) the absence in Fegatella of the long hollow sterile lobes which are 
so characteristic of M archantia ; (2) the development in Fegatella of a single 
archegonium from each growing-point, instead of the group of archegonia 
found in Marchantia between each pair of sterile lobes. 
The higher Marchantiaceae, i. e. those having a stalked female recep- 
tacle, were divided by Leitgeb (1881, p. 49) into three sections, to which 
he gave the names Astroporae, Operculatae, and Compositae, and this 
