421 
Lang.— On the Morphology of Cyathodium . 
rise to the row of cells forming the rest of the foot and to the base of the 
wall of the capsule. The lower of the two cells of the upper half produces 
the greater part of the capsule and all the sporogenous tissue. After the 
quadrant divisions in this segment periclinal walls cut off the cells of 
the capsule wall. The central cells divide further and ultimately separate 
as the spore-mother-cells. From the uppermost segment of the embryo the 
upper two tiers of cells in the apical disk are derived. The lowest tier can, 
however, be traced back to the upper portion of the sporogenous tissue. 
A single layer of the latter at the upper limit of the group does not separate 
into spore-mother-cells, but remains as a continuous layer in contact with 
the uppermost sterile segment (Fig. 43), and forms part of the apical disk. 
A comparison of Figs. 40 and 41, in which the limits between the original 
segments are clearly recognizable, with Fig. 39 will enable the course of the 
segmentation to be followed ; Fig. 42 shows the quadrant and periclinal 
divisions in the sporogenous segment. 
The actual size of the sporogonia and of the spores contained in them 
presents some features of interest. Figs. 48 and 49 are outlines, drawn 
to the same scale, of longitudinal sections through the sporogonia of the 
two forms investigated. They are of practically the same age. In both 
cases the cells of the upper part of the wall had well-developed brown rings, 
and the walls of the spores and elaters were also thickened. The calyptra, 
however, was not ruptured and (as shown by measurements of opened 
sporogonia) the full size had not been attained. This does not, however, 
obscure the somewhat surprising fact that, while the sporogonium of 
C. cavernarum is much smaller than that of C. foetidissimum , the spores 
of the former are considerably larger. The sporogonium of C. foetidissimum 
figured (Fig. 48) was 625 /x in length, the capsule being 525 /x ; the length of 
mature capsules was estimated as 800 ju. The sporogonium of C. caver - 
narum figured was 325 M in length, the capsule being 250 /x ; the mature 
capsule was about 400 /x long. Mature spores of C. foetidissimum were about 
40 /x in diameter, or, including the projecting thickenings of the wall, nearly 
50 /x. Those of C. cavernarum were 60 /x in diameter, or, including the 
thickenings, 63 /x. This association of proportionally large spores with 
a very small capsule, which has probably resulted from a process of 
reduction, is of interest for comparison with Archidium. In this genus 
of Mosses, as is well known, very large spores are found in a small and 
possibly reduced sporogonium. 
Conclusion. 
If we compare Cyathodium with the other Marchantiaceae in the light 
of the additional facts as to its vegetative structure, the structure of the 
antheridium, and the development of the sporogonium detailed above, the 
only possible conclusion seems to be that they confirm the close relationship 
