420 
Lang . — On the Morphology of Cyalhodium. 
A mature sporogonium is represented in almost median section 
in Fig. 24. Unfortunately the section just missed the apical disk (cf. 
Fig. 20). The spores are thick-walled, the exospore bearing rounded 
tubercles, and between them are the free elaters. The cells of the lower 
two-thirds of the wall of the capsule have their internal walls slightly 
thickened and of a brown colour, but have no thickenings on the vertical 
walls. Those of the upper third bear complete rings, usually thicker to the 
outside. The apical disk is apparently thrown off entire at dehiscence, for 
the open sporogonia had eight blunt teeth formed by the splitting of the 
upper third of the capsule wall. The sporogonium is protected until 
maturity by the calyptra, which keeps pace with its increase in size and 
is not ruptured until the time of dehiscence. More than one sporogonium 
may be developed from the group of archegonia, and thus be enclosed 
within the common involucre. 
C. cavernarum . The material showing younger stages of the sporo- 
gonium of this species was more abundant, and enabled the development to 
be followed nearly continuously. On account of the extremely small size 
of the sporogonium this could be done with a precision almost impossible 
in the case of more bulky sporogonia, and the definite delimitation of the 
several regions may perhaps prove of use for comparison with the latter. 
In the mature sporogonium (Fig. 44) we can distinguish a cylindrical 
foot, consisting of a row of cells and terminating below in a pair of larger 
cells, which grow out into absorbent processes (Fig. 46). The wall of the 
capsule, which contains relatively few large spores and some elaters, is com- 
posed of a single layer of cells. The cells of the upper third of the wall 
have ring-shaped thickenings, while those forming the lower two-thirds are 
thin-walled and of peculiar appearance. They are densely packed with 
starch grains and the nucleus in each is prominent and had often undergone 
fragmentation (Fig. 47). The appearance of these cells at once suggests 
a comparison with tapetal cells, and they have probably a nutritive function. 
At the summit of the capsule is the apical disk, the position of which 
is seen in Fig. 44, while its structure in median section is better shown in 
the adjoining section (Fig. 45). It consists of two series of four cells each, 
the cells being superposed, and of an inner layer of eight cells. The disk 
projects into the cavity of the capsule. The mode of opening of the sporo- 
gonium is similar to that of C. foetidissimum , and has been described and 
figured by Leitgeb. The spores have a dark brown exosporium, closely 
covered with spiny projections. 
The first division in the embryo is transverse, and, unlike what usually 
happens in the Marchantiaceae, this is followed by transverse walls in both 
upper and lower segments (Figs. 38, 39). From the lowest cell of this row 
of four is derived the basal group of cells (usually two in number) which 
bear the processes. The upper cell of the lower half of the embryo gives 
