IOO 
Cavers.— On the S true hire and 
chambers, which arise in essentially the same manner as those of the 
thallus. The dorsal portion of the receptacle thus acquires a spongy 
character, whilst the ventral portion consists of compact colourless tissue 
with mucilage-sacs and oil-cells. The air-chambers are at first long and 
narrow, each opening above by a pore which is surrounded by three or 
four superposed rings of cells (PL VII, Fig. 31, /.). Pores of this type, 
generally termed ‘ compound ’ or ‘ barrel-shaped/ are also found on the 
female receptacle, where they are more highly developed. Each antheridium 
becomes sunk in a deep cavity, formed in essentially the same manner as 
the air-chambers (PI. VII, Figs. 29-31). As the antheridium grows in size, 
its cavity becomes flask-shaped, with a long narrow canal opening above on 
the surface of the receptacle by a very narrow pore (PI. VII, Fig. 30). In 
consequence of the lateral pressure exerted by the growing antheridia, the 
air-chambers between the antheridial cavities become greatly compressed 
below, but in the upper portion of the receptacle they remain as wide 
spaces, each opening above by a barrel-shaped pore. The cells lining the 
air-chambers grow out here and there into filaments resembling those found 
in the air-chambers of the thallus. The male receptacle is therefore well 
provided with assimilating tissue. Water is taken up by means of the 
numerous smooth and tuberculate rhizoids which spring from the lower 
surface of the receptacle (PI. VII, Fig. 30) ; part of this water is given off as 
vapour by the green cells lining the air-chambers, whilst large quantities 
can be stored up in the colourless cells of the ventral tissue. The margin 
of the receptacle is beset with scales derived from the growing-points, and 
the tissue of the thallus behind and on either side of the receptacle grows 
up to form a partial sheath. 
In several cases the writer has found two antheridia occupying a 
common cavity, the sides along which they were in contact being strongly 
flattened (Fig. 29). The two antheridia were found, in those cases where 
fresh sections were examined, to be so closely joined that it was impossible 
to separate them without injury, and in a few cases the appearance of young 
pairs of antheridia strongly suggested the possibility of their having arisen 
from a common mother-cell. Similar examples of paired antheridia have 
been described by Leitgeb (1879, p. 67, Taf. 8, Fig. 17) for Sphaerocarpus , 
and by Campbell (1896, p. 500) for Geothallus , but they do not appear 
to have been hitherto recorded in the Marchantiaceae. 
The cells forming the wall become mucilaginous, and on adding water 
to a ripe antheridium, these cells become swollen. The delicate walls of 
the antherozoid mother-cells also swell up in the same manner and 
ultimately become dissolved. Mucilage is also formed by a number of 
long club-shaped cells (paraphyses) which grow up from the bottom of each 
antheridial cavity, around the base of the antheridium. In consequence of 
the pressure set up, the antheridial cavities eventually come to be separated 
