168 
Berridge and Sanday. 
The walls of these cells are very thin, but in deeply stained 
sections variations in their thickness are just perceptible along the 
cut edges. Also in surface view they show thin areas just like 
those figured in Miss Stopes, and Dr. Fujii’s paper (3), while fine 
plasmic threads are constantly observed at points where the cyto¬ 
plasm of the egg has separated from the wall. In the fully-grown, 
but unfertilized egg, colourless drops of a viscous appearance seem 
to be oozing through it into the archegonium ; it is only after the 
time of fertilization that proteid vacuoles containing granules are 
seen to be passing through, and soon after the wall breaks up 
entirely in many places and allows the jacket nuclei to escape. 
Just at this time a curved row of pro-embryonal cells is found, 
in the majority of ovules examined; these are similar to those 
developed from the daughter-nuclei of the oospore, that is, they 
possess large nuclei surrounded by radiating strands of cyto¬ 
plasm and are bounded by delicate cell-walls, but they are situated 
in the middle and upper part of the egg-cell, and when first formed 
contain ill-defined masses of fusing nuclei, very different in 
appearance from the well-marked daughters of the fusion nucleus. 
Many circumstances seem to indicate that these pro-embryos arise 
from the escaped jacket nuclei and not from the fertilized egg 
nucleus. They are always found lying near empty jacket cells, and 
are always in contact on one side with the wall of the archegonium. 
One slide showed an archegonium containing two series of pro- 
emhryos, one in the pointed base corresponding to that formed by 
what we have called the “normal” method of embryogeny, the 
other lying above it corresponding to the series just described 
(Fig. 16, cf. Fig. 14). The first or normal series of pro-embryos is 
evidently dwindling away, the second upper series is still in course 
of formation. At one point nuclei can be seen passing out of 
adjacent jacket cells to fill a gap in this series (Fig. 17), while at 
another the pro-embryo is simply an out-growth of one jacket cell 
lying in a row of others which are in a dying condition (Fig. 18). 
The view that these pro-embryonal cells are formed by jacket 
cell nuclei, is supported by the fact that similar pro-embryos are 
frequently found within the jacket cells themselves, even when not 
adjacent to the archegonia. Such a pro-embryo is shown in Fig. 19, 
bounded on three sides by the disorganizing remains of an un¬ 
fertilized archegonium and of the same and other jacket cells, and 
on the fourth by the vacuolate cells of the undifferentiated endo¬ 
sperm. Just prior to the formation of these pro-emhryos, migration 
