51 : 
vertical one at right angles, so that when the antheridium is seen 
from above the central cell appears divided into four, arranged 
like the quadrants of a circle. These are followed by others un- 
til the full number, varying a good deal, even in the same species, 
is formed. 
The central cell now consists of a tissue composed of small, 
thin-walled polyhedral cells, each one having a small but distinct 
nucleus. The antherozoids are derived directly from the nucleus, 
which, previous to their formation, becomes indistinct, but does 
not actually disappear. As soon as it can be definitely observed 
again, it is seen to have increased in size and to have become 
curved (Fig. 9.) It rapidly increases in size, becoming at the 
- same time more curved, until it finally comes to occupy nearly 
the whole cell, some granular protoplasm, however, remaining 
between the coils, especially toward the centre of the cell. 
When the antherozoids are fully grown, the sperm-cells have in- 
creased in size so as to crowd upon the parietal cells, and occupy 
nearly the whole space of the antheridium, which is now nearly 
globular (Fig. 5.) . 
The walls between the sperm- -cells now undergo a change, - 
becoming mucilaginous, so that when water is applied they dis- 
solve, allowing the antherozoids to become separated, but enough 
of the wall remains, so that they are still enclosed in a delicate 
membrane. The dissolution of the division walls is accompanied 
by very evident movements of the contents of the antheridium. 
When the antherozoids are ready to escape, the parietal cells 
absorb water with great avidity, until the pressure becomes so 
great as to ‘rupture the wall of the antheridium. This usually 
occurs between the middle and top cell, the latter being torn 
open; or sometimes simply through a fissure in the cap-cell. As 
the parietal cells absorb the water they become very much dis- 
tended, pressing in on the mass of sperm-cells, which are thus 
forced out through the opening. In cases where the first wall in 
the antheridium did not extend to the base, it. was forced up by — 
the absorption of water in the cell beneath, so as to nearly oblit- 
erate the cavity of the antheridium. : 
The antherozoids remain for a few moments after their escape 
enclosed in the remains of the wall of the mother-cell, but this is 
