240 Campbell.— Contributions to the 
appears triangular, or nearly so, in outline, the walls bounding 
it meeting so as to enclose a nearly regular tetrahedron. The 
nucleus is also evidently larger than those of the surrounding 
cells. A notable point connected with the archegonium, and 
also true of the later ones, is the large size of the mother- 
cell as compared with that of the archegonium of most pteri- 
dophytes. Of the other pteridophytes, the Marattiaceae 1 
approach most nearly to Isoetes , as they do in the structure 
of the mature archegonium. 
The development of the first as well as the later archegonia 
is the same, and follows closely that of the Filicineae, showing 
especially close resemblances to the Marattiaceae. The 
mother-cell (Fig. 13, ci) first divides by a transverse wall into 
two cells, of which the outer smaller one gives rise to the neck of 
the archegonium, the inner larger one to the central cell and the 
neck-canal-cell. The first division in the inner cell is parallel 
to the first wall in the archegonium mother-cell, which thus 
becomes divided into three cells placed one above another (Fig. 
14). The contents of these cells are quite similar and the 
nuclei large and distinct. The next divisions occur in the 
neck-cell, which is divided by vertical walls, at right-angles to 
each other, into four nearly equal cells. These mark the four 
rows of cells composing the neck. Each of the neck cells next 
undergoes division by a transverse wall into two, and each of 
the latter in the same way into two more, so that the mature 
archegonium has a neck composed of four rows, each com- 
posed of four cells (Figs. 1 6, 17). 
Almost simultaneously with the first transverse divisions of 
the neck-cells, the central cell has cut off from its upper part 
the ventral canal-cell (Figs. 15, 16, b), which is larger than is 
common, being the whole breadth of the central cell. In the 
meantime the neck-canal-cell ( h ) has pushed up between the 
neck-cells, but while very broad, is relatively much shorter 
than usual. 
The neck-canal-cell has at first a single nucleus, but this, 
1 Jonkman, La generation sexuee des Marattiacees, Figs. 99-105. 
