4i7 
Lang . — On the Morphology of Cyathodium . 
been able to study the development to some extent. The young antheri- 
diophore is first recognizable as a projecting disk of tissue just below the 
margin of the thallus in the apical depression (Figs. 31, 32). Possibly it 
may in some cases originate from the apical cell itself, but the arrange- 
ment of its cells as seen in surface view, taken together with the positions 
in which the mature antheridiophores were found, makes it clear that this is 
not always or usually the case. It appears rather to originate from one, 
two, or several cells of the anterior margin close to the actual apex. In the 
specimen drawn in Fig. 31 two such cells seem to have been involved, and 
in that in Fig. 32 three segments can be traced. At this stage the antheridia 
have not yet appeared, but the septa between the chambers have commenced 
to grow up (Fig. 33). When the antheridia have developed (Figs. 29, 30) 
they are found to stand in a regular series, the youngest being next to the 
margin of the thallus and the oldest being those that stood closest to 
the posterior border of the young antheridiophore. These facts taken 
together dispose me to regard the antheridiophore as the equivalent of 
a much reduced ventral branch, while placing the succession of the antheridia 
in relation not to the apical growth of the branch, but to the marginal 
extension of the group of cells forming the rudiment of the antheridiophore. 
I have, unfortunately, not been able to study the development of the male 
branch in Targionia and C. foetidissimum , comparison of which may be 
expected to throw further light on the question. 
In both species of Cyathodium the archegonia stand on the morpho- 
logically upper surface of the thallus, any branch of which may give rise to 
a group of archegonia. The actual position in which the archegonia come 
to stand and the mode of development of the involucre around the group 
differ to such an extent in the two forms that their separate description 
is necessary. 
In C. foetidissimum the state of things is closely comparable to what is 
found in Targionia. By displacement of the apical region the archegonia 
come to stand on what is apparently the under surface of the branch, though 
morphologically it is a part of the upper surface. Sometimes there is only 
one group of archegonia in front of the antheridiophore, the position of 
which has been described above. Usually, however, the apex of the 
thallus, after the male branch has been laid down, branches dichotomously, 
though this dichotomy does not affect the general outline, and is evident 
simply by the formation of two groups of archegonia instead of a single 
one. Archegonia may also occur on a branch which does not bear an 
antheridiophore. The archegonial groups are at first protected by large 
ventral scales. At this stage (Fig. 9) the displaced region of the upper 
surface has a V-shaped outline, the initial cell being at the point of the V, 
while the arms of the latter correspond to the margin of the thallus, i. e. to 
the line of junction of dorsal and ventral surfaces (Fig. 13). The archegonia 
