Rhabdonia tenera , J . Ag. 419 
It is interesting to note how the Liverworts, responding 
to terrestrial conditions, have in the higher forms raised 
the sporophyte above the thallus to secure a better dis- 
semination of the spores, while in the Florideae the opposite 
tendency has been manifested; protection has been the 
determining factor, and the cystocarp has, in the higher 
forms, been buried beneath the surface of the frond much 
as the sporophyte is in the lower Hepaticae. The formation 
of a protective covering by the sporophyte is peculiar to the 
Liverworts ; and, while not a character of fundamental impor- 
tance, shows a higher degree of development. 
Tetrasporangia. 
The tetrasporangia develop directly from the outermost 
cells of the cortex (i. e. from apical cells of the cortical 
filaments). They become enlarged, and densely filled with 
protoplasm ; the nucleus divides into two and then into four ; 
the protoplasm by ‘ free cell-formation * separates into four 
masses somewhat rounded off from each other, but not 
separated by cell-walls. In this condition they remain 
until they escape from the tetrasporangium or commence 
to germinate in position. 
The tetrasporangium, during its growth, encroaches on the 
surrounding cells, and distorts them ; when mature it often 
has a double wall (Fig. 6), the inner layer of which is thinner 
and somewhat denser than the outer. The tetraspores escape 
by the rupture of the gelatinous wall of the sporangium ; 
they remain for a short time enclosed in a delicate membrane ; 
this is then dissolved, and the spores separate from each 
other, become spherical, and finally become attached to the 
substratum and germinate. The germination proceeds exactly 
like that of the carpospores, the first walls being laid down 
without any regular arrangement. 
Germination of Tetraspores. 
The older tetrasporic plants commonly bear on the older 
portions of the plant numerous short simple proliferations, 
