I 72 
Berridge and Sunday. 
“Alveoli ’’are formed after a very large number of nuclear divi¬ 
sions, and the archegonial region already begins to be differentiated. 
Cell-division occurs much more freely in the lower than in the 
upper part of the embryo-sac. The archegonial region becomes a 
mass of archegonium initials and jacket cells, distinguishable from 
the surrounding cells by their large nuclei and richness of cell- 
contents. 
The pollen-chamber is formed by the breaking down, first of 
hypodermal, and then of epidermal cells at the apex of the 
prothallium. At its base the apical cells of the prothallium are 
exposed. 
The species appears to be anemophilous though insects may 
occasionally pollinate the ovules. The grains are probably drawn 
down the micropyle into the pollen-chamber by the gradual drying 
up of the liquid secreted at this time. 
The archegonia number from five to eight; until the central 
cell is full-grown the nucleus remains at the apex. The ventral 
canal nucleus appears to separate from the egg-nucleus by a process 
of direct division shortly before fertilization ; no wall is formed 
between them. 
The pollen-tube discharges the two male gametes enclosed in a 
common cytoplasmic sheath into the egg. The functional gamete 
slips from the sheathand passes to the egg-nucleus, but in most 
cases fusion does not appear to have occurred, and no case of the 
entry of the sperm into the egg-nucleus was found. 
Fertilization, however, probably occurs occasionally, for arche¬ 
gonia are found containing nuclei which can only arise from the 
egg; some of these pass to the base of the archegonium and there 
form pro-embryonal cells. These form long suspensors, bearing 
embryos at their tips. Most of the pro-embryos, however, are 
formed by abnormal development from the jacket-cell nuclei. 
The jacket cells arise at the same time as the central cells; at 
first they increase in number by indirect division. Later the nucleus 
divides by direct division and the bi-nucleate cell grows considerably 
larger and becomes full of food material. The wall of the egg-cell 
gradually becomes more and more permeable to food material, and 
linally breaks down, allowing the jacket nuclei to escape. 
These nuclei fuse together within the egg-cell and give rise to 
pro-embryos. 
In some cases the pro-embryos are merely enlarged jacket-cells 
which project into the archegonium. 
