1915] BRYAN—ARCHEGONIUM OF SPHAGNUM SUBSECUNDUM 47 
THE COVER CELL 
Figs. 18 and 19 represent typical cases in the appearance of 
the archegonium with cover cell and central cell formed. It will 
be noted that the two cover cells differ in size. This is due to the 
peculiar shape of the cover cell, coupled with the direction of the 
cut. In fig. 18 the cut is median through the long diameter; in 
fig. 19 through a shorter diameter. This may be more clearly 
understood by an examination of the cover cells as shown in 
transverse sections (figs. 53~55). 
It is important to note that the cover cell may divide by a 
vertical wall into two almost equal segments before the division 
of the central cell takes place (figs. 21, 54). But more important 
still is the evidence that by the time the central cell has completed 
its division into primary neck canal cell and primary ventral 
cell, the cover cell has at least become divided by a vertical wall 
into two almost equal segments (figs. 22, 24), and in some cases 
has formed a quadrant of cells (figs. 23, 56). The division lines 
between the cells of the cover and the outer cells of the neck are 
clearly marked and easy to follow in the younger stages. Thus 
in figs. 29~32 the cover is literally the cap of the archegonium, and 
in each case contains 6 cells (three each in median longitudinal 
section, as illustrated). In fig. 33 the cover consists of 8 cells. 
However, in the older stages the cells of the cover and the neck 
usually merge so insensibly that the two cannot be separated with 
any degree of certainty. Hence no accurate statement as to the 
final number of cells produced by the cover can be made. 
From the foregoing facts it is evident that the cover cell divides 
early by a vertical wall into two almost equal segments. Sub- 
sequent vertical divisions in each of these segments produce a 
plate of cells, 8 or more in number, which covers the apex of the 
archegonium and in mature forms merges insensibly with the 
upper cells of the neck. There is not the slightest evidence to 
show that the cover cell cuts off any basal segments. 
THE CENTRAL CELL 
The division of the central cell into primary neck canal cell and 
primary ventral cell is shown in figs. 20 and 21. The primary 
