50 BOTANICAL GAZETTE. [ March, 
true ferns in the indistinctness of the layers of cells representing 
the successive segments of the apical cell, all traces of the strati- 
fication so couspicuous in true ferns being very early lost. Oc- 
cupying the center of the root is a cylinder of procambium cells, 
and surrounding this, several rows of broader cells, with inter- 
cellular spaces between their lateral walls. On account of the 
air occupying the spaces, this zone of cells is very conspicuous 
when the section is mounted in water. Lying outside of these 
cells is a second zone of smaller cells destitute of intercellular 
spaces, and surrounding the whole is the epidermis whose cell- 
walls, very early, become brown in color, and form a continuous 
hin brown covering over the end of the root. Some of the cor- 
tical cells lying immediately underneath later have their walls 
similarly changed. 
The apical cell (figure 1. a) is a nearly equilateral tetrahe- 
dron in form, and the succession of segments seems to be per- 
fectly regular. Each segment is formed by a wall parallel to 
one of the faces of the apical cell, the cell thus formed being 
tabular, with the broader faces triangular. The cap-cell is the 
last formed of each cycle of segments, and differs in its subse- 
quent divisions from the three lateral segments. Each of the 
latter is first divided into two nearly equal cells by a radial wall 
gure 2.a). In each of the cells thus formed a tangetial wall 
arises, dividing it into an inner and an outer cell, the former be- 
ing the larger; and very soon after, the inner cell becomes fur- 
ther divided by a second tangential wall into two nearly equal 
cells. Of the three cells into which each half of the original 
segment is now divided, the inner one gives rise to the central 
rocambium cylinder of the root; the middle one to the ground 
tissue lying next the procambium, and probably to the whole, or 
at any rate to a large part of the cortical parenchyma; from the 
outer cell, the epidermis and possibly part of the cortical tissue. 
I was unable to determine positively whether or not the outer 
cell underwent any further division by walls parallel to the first 
wall, that is, whether the cells derived from. this outer cell 
formed more than one layer, or whether all the subsequent di- 
vision walls were perpendicular to that first formed. 
In the segments from which the root-cap is formed, the first 
wall, as seen from above (figure 3. 1), is parallel to one of the 
sides of the triangular cell, dividing it into two unequal cells, an 
elongated four-sided, and a triangular one. The former is 
divided into two by a wall perpendicular to the first (figure 3- 
11), before the other is divided. For a short time walls are 
formed only at right angles to the broad faces of the segment, as 
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