60 Campbell. — On the Prothallium and Embryo of 
The cells thus cut off form the basal part of the antheridium. 
Sometimes when the number is large, a pedicel is formed, 
and the antheridium projects strongly from the prothallium. 
(Fig. 60 shows an extreme case.) The upper segments are 
shallower, and when the full number is formed, a dome-shaped 
wall (Fig. 36) arises in the upper cell, which meets the basal 
cells and encloses a nearly tetrahedral cell from which the 
sperm-cells are formed. (This cell is the shaded cell in 
Fig. 36.) 
The central cell is quite destitute of chlorophyll, and has 
a large distinct nucleus imbedded in dense highly refractive 
protoplasm. 
The subsequent divisions of the outer dome-shaped cell are 
not always exactly the same, but the differences are not im- 
portant. In it are first formed two or three walls running 
more or less obliquely over the apex. Either at the top, or 
at one side, the last-formed walls meet so as to enclose a small 
cell (Figs. 39, 41 o), that marks the point where the ripe 
antheridium opens. This cell is often triangular in shape, 
and in form and position very much resembles the opercular 
cell of the Marattiaceae h About the time that the first 
division in the peripheral cell occurs, begins the division of 
the central cell. This corresponds closely with that in other 
ferns. The first wall is nearly vertical, and is followed by 
a second at right angles to it, so that the central cell, seen 
from above, is divided into four nearly equal cells (Fig. 42). 
A formation of nearly regular octants is often perceptible, 
and in these anticlinal walls are formed ; but soon no regular 
arrangement can be traced, and a mass of polyhedral cells 
with dense contents fills the central part of the antheridium. 
Chlorophyll is present in the peripheral cells, but the granules 
are small and scattered, so that the cells appear almost 
colourless. The nuclei are distinct and the division-walls 
conspicuous. In the earlier stages, the division-walls between 
the central cells are thin and not very evident, but about the 
1 Jonkman, La Generation sexuee des Marattiacees ; Archives Neerlandaises, 
T. XV. PI. VII, figs. 65-72. 
