Osmunda claytoniana , A., and O. cinnamomea , L. 6g 
nucleus had contracted and was noticeably smaller than in the 
younger egg-cell. This ‘ polar body ’ was noticed several 
times, and in these cases the ventral canal-cell partially dis- 
organized, and the two nuclei of the other neck-cells, were 
unmistakeable. As the actual division of the nucleus of the 
egg was not seen, of course it cannot be stated positively that 
the body in question is a true polar body; but the apparent 
diminution of the nucleus of the ripe egg, and the behaviour 
of the body toward staining agents, make it extremely prob- 
able that this is the case. Admitting that we have to do 
here with a true polar body, of course it is an open question 
whether the ventral canal-cell is also to be so regarded, or if it 
is merely the physiological equivalent of the other neck-cells ; 
i. e. as simply concerned in the opening of the archegonium, 
and helping to form the channel down to the egg. 
At maturity the division-walls of the central row of cells, 
and probably also the inner walls, in part, of the neck-cells, 
become mucilaginous, and the opening of the archegonium 
follows very quickly on being put into water, especially if the 
prothalha have been kept rather dry for a few days. The 
neck-cells become very turgid, and as they separate the four 
rows diverge widely, and usually some of the upper cells be- 
come entirely detached. At the same time the remains of 
the canal-cells are forced out (Fig. 72). 
Owing to the overlying cells, the egg is only vaguely seen, 
and in order to study it satisfactorily, sections must be made. 
In sections of the fresh archegonium, the egg appears colour- 
less, and shows the receptive spot and nucleus. In microtome- 
sections of chromic acid material, it is seen that the contents 
are not uniform, but that the lower part of the egg shows a 
reticulate arrangement of the granular protoplasm, as if there 
were vacuoles present. The upper part, about one-third, is 
almost entirely free from granules, and constitutes the re- 
ceptive spot. The nucleus is smaller than in the younger 
egg, and contains usually a single nucleolus, and is tolerably 
rich in chromatin. 
