8 Campbell . — Observations on the Development 
the axial row of cells, which Hofmeister 1 regarded as the 
whole archegonium, really represents only the central row of 
the typical bryophytic archegonium, as this axial row of cells 
is cut out by walls which correspond to those in the arche- 
gonium-mother-cell of other Bryophytes. It seems to me 
from a careful study of Marattia , as well as other ferns, that 
this is the case in the Pteridophytes, and that what is ordinarily 
called the mother-cell of the archegonium, is homologous, not 
with the mother-cell of the archegonium of a Liverwort or 
Moss, but with the central row of cells only. The cells which 
are later cut off from the adjacent prothallium-cells (Fig. 16- 
1 7, m) probably represent the peripheral cells of the arche- 
gonium. The neck of the archegonium, too, here seemed to 
be of a totally different type. In all Pteridophytes it is 
composed of four rows of cells, derived from the cross-divisions 
of the outermost of the three original cells. Examining the 
Bryophytes, we find two distinct types of archegonium, that 
of the Liverworts and that of the Mosses : while in both the 
neck is composed of six, occasionally five, outer rows of cells, in 
the Liverworts at a very early stage the upper cell of the axial 
series divides by cross-walls into four and forms the upper 
cells of the neck : in the Mosses, on the contrary, the upper 
cell functions for a long time as an apical cell before its final 
cross-division, and adds new cells both to the outer cells and 
to the canal-cells. Now the question is, how was the 4-rowed 
neck of the pteridophytic archegonium derived from the 
6-rowed neck of that of the Bryophytes ? The answer 
probably is, that it represents a development of the four 
terminal cells only. These in Liverworts usually undergo 
a single division, or occasionally more than one. If we accept 
this view, it will bring still closer together the eusporangiate 
ferns and the Anthoceroteae, and the latter will become of still 
more importance in the study of the phylogeny of the ferns. 
We shall then assume that the Eusporangiatae are derived 
from Liverworts in which, as in Anthoceros , the archegonium 
was completely sunk in the thallus, and that from the four 
1 Hofmeister, Higher Cryptogam ia, p. 9. 
