239 
Rickett.—Fertilization in Sphaerocarpos. 
egg or of the free surface of the cells of the embryo than appears at this 
time. Meyer (1911) describes and figures the egg of Corsinia marchantioides 
as forming about itself a distinct membrane after receiving the antherozoid. 
Comparing his figure with the fertilized egg of 
Sphaerocarpos , the egg of the latter takes up far 
less room in the venter, and what seems to corre¬ 
spond to the £ fertilization membrane ’ in Corsinia 
is the heavily staining mucilaginous material 
that filled the cavity of the venter and the neck 
during the first phase of fertilization and that 
remains as a dense layer appressed to the inner 
wall of the venter and filling the neck (Text- 
fig. 2 ). In a subsequent paper Meyer (1913) 
again refers to, and figures, the fertilization 
membrane, this time in Plagiochasma rupestre. 
Here the resemblance is even stronger to what 
I have seen in Sphaerocarpos , and the suspicion 
seems justified that the so-called ‘membrane’ 
may really be the mucilaginous material of the 
venter, which looks like a membrane belonging 
to the egg only when the latter completely 
fills the venter. 
A fertilization membrane has been described Text-fig. 2. Archego- 
for several other Liverworts. Kny (1866) figures and containing an egg in the 
and describes a fertilized egg of Riccia sorocarpa fourth phase of fertilization. 
Thirty-six hours after flooding. 
as surrounded by a fairly thick layer or mem- x 320. 
brane. Garber (1904) says that the egg of Riccia 
natans surrounds itself with a membrane immediately after fertilization. The 
same is reported for Fegatella conica by Cavers (1904), and for Targonia 
hypophylla by Campbell (1918). Cavers says that the membrane is of 
cellulose. These authors do not, however, go into details on the subject. 
The position of the male nucleus during this phase is in general the 
same as in previous phases, but in one instance the two nuclei were seen in 
contact. 
Fourth Phase. 
There now begins a marked change in the male nucleus. The condition 
mentioned above, in which the mass of this nucleus seems to be granular in 
structure, is more often seen, and often the structure is looser, so that distinct 
granules may sometimes be made out, with lighter areas between them 
(Figs. 10 and 11 ). At the same time, threads project from the edge of the 
dense part of the nucleus and extend across the clear space to the nuclear 
membrane (Fig. 8). Sometimes there are but one or two of these threads, 
R 
