Life-History of Isoetes . 241 
at least in some instances, divides as in most ferns, but there 
is no division-wall formed (Fig. 17). 
As the archegonium approaches maturity, the neck-cells 
elongate somewhat, and the two upper tiers project above the 
surface of the prothallium (Fig. 16). Shortly before opening, 
the walls of the canal-cells, as usual, become disorganised, and 
with their contents form a mucilaginous mass which is expelled 
when the archegonium opens. At the same time the contents 
of the mother-cell of the egg-cell contract and become nearly 
globular. The act of opening of the archegonium was not 
observed, but stages shortly before and after were met with. 
The egg-cell (Fig. 18, 0 ) is a large round or oval naked 
cell with a large and clearly marked nucleus, having a very 
large nucleolus that stains with great intensity; but besides 
the nucleolus there seems to be but little chromatin. The 
upper part (about one-third) of the egg is composed of hyaline 
protoplasm, exhibiting a faintly reticulate structure, and forms 
the c receptive spot.’ The lower part, surrounding the nucleus, 
is filled with granules, and stains strongly with gentian-violet. 
Owing to the small size of the spermatozoids and the great 
difficulty of getting satisfactory sections of ripe archegonia, the 
actual process of fertilization was not seen, and I am not pre- 
pared to state positively what the first results of the process 
are. In one or two cases noted, where the egg had apparently 
been recently fertilized, the receptive spot had disappeared and 
the protoplasm had become uniformly granular throughout. 
The ripe archegonium closely resembles that of the Marat- 
tiaceae. It is sunk in the prothallium except the two upper 
tiers of neck-cells, and both in this respect, as well as the 
very broad canal-cells, resembles closely Jonk man’s figures 1 
of Angiopteris and Marattia . The egg-cell, however, is 
relatively much larger. Owing to the small increase in size, 
during its growth, there is very little displacement of the cells 
of the archegonium and its limits are very definite. 
In Isoetes lacustris , according to Hofmeister 2 , only one 
archegonium is formed at first, and if this is fertilized no 
2 Loc. cit., p. 340. 
1 Loc. cit. 
