5 1 6 Black . — The Morphology of Riccia Frostii , Aust. 
more or less cubical until the last division, which is a diagonal one, forming 
two triangular cells. Kny in Marchantia and Campbell in Fimbriaria 
report this final division without a cell-wall, as does Lewis (31) for Riccio- 
carpus natans. Durand (14) states that in slides stained with Delafield's 
haematoxylin the diagonal walls in Marchantia show distinctly in some cells, 
but seem to disappear early. The diagonal cell-walls were not found in Riccia 
Frostii , but at this stage in the antheridium the cell-walls appear to undergo 
a change, so that their detection may be a question of stage in develop- 
ment. The mature antheridium of Riccia Frostii has a short stalk, and 
is oval, with a flat base and rounded apex. The apex may be conical in 
young antheridia (Fig. is). The size of the mature antheridium was 
found to vary ; comparatively small antheridia were found with mature 
spermatozoids. 
Before the sperms have been discharged from an antheridium they all 
eventually reach the same state of maturity and lie in a common cavity. 
All cell-walls in the antheridium disappear, and probably add to the semi- 
fluid contents of the antheridium. Several writers have observed the 
explosive discharge of sperms in various Liverworts. • In Fegatella conica 
this was first observed by Thuret (40). King (29) and Cavers (10) have 
also studied the explosive discharge of sperms in Fegatella , and Peirce (38) 
in Asterella. While the discharge of the spermatozoids was not observed 
in Riccia Frostii , the following conditions point to their discharge as 
probably of an explosive nature. Antheridia when mature are filled with 
sperms, lying free in the cavity surrounded by the semi-fluid substance. 
The antheridium wall appears normal. In antheridia, where the sperms 
have been partly discharged, the cells in the wall of the antheridium are 
greatly distended inward. It would seem as if the pressure exerted by 
these cells would be sufficient to forcibly expel the spermatozoids. Antheridia 
are found emptied of their contents without any disturbance to surrounding 
cells, showing that the release of the spermatozoids is not due to a breaking 
down of tissue. 
The complete account of the development of the archegonium in 
Riccia Bischoffii , by Janczewski (27), has been little modified by later 
investigators. The development of the archegonium is in general like that 
of the Liverwort archegonium described by Campbell, and by Garber (22) and 
Lewis for Ricciocarpus natans . In the paper by Durand (14) on Marchantia 
polymorphya , the steps in the development of the archegonium are so clearly 
presented and in such sequence that it is unnecessary to repeat them here. 
Various stages are seen in Figs. 14, 15, and 1 6 . 
Actual fertilization was not observed. However, the sperm nucleus 
was observed in the egg-cell and in juxtaposition to the egg nucleus 
(Fig. 17). The fertilized egg probably undergoes a period of rest, as 
innumerable archegonia were found with the egg in the condition shown in 
