1922] DUPLER—REBOULIA 149 
in the epibasal portion. Haupt thinks oblique walls do not occur 
at this stage or later. It seems to the writer that the evidence for 
the occasional occurrence of oblique walls is conclusive. 
The occurrence of a filamentous embryo in Reboulia agrees 
with the embryo described for Plagiochasma (STARR 17), Targionia 
(O’KEEFE 16), Geothallus, and Sphaerocarpus (CAMPBELL), as well 
as practically all the Jungermanniales. Quadrant formation by 
walls vertical to the first wall occurs in Riccia (CAMPBELL 1), in 
Marchantia, as given by a number of writers, DuRAND’s account 
being the most complete, Conocephalum (CAVERS 2), and Fimbriaria 
californica (CAMPBELL). KiENiTz-GERLOFF made a similar claim | 
for Grimaldia and Preissia, but did not have the early stages. 
GARBER found occasionally a row of three cells in Riccia natans, 
although the quadrant form was the rule. In the following ac- 
count the innermost cell of the filament of four cells will be desig- 
nated as the basal cell, the outermost as the apical cell. 
VERTICAL WALL FORMATION.—Vertical walls now begin to form 
in the young embryo. According to Haupt, “these vertical divi- 
sions begin at the lower end of the embryo, a feature which is also 
noted by WoopBuRN’s figures.’’ This probably is‘the general rule, 
and is evidenced by Haupt’s figures, which show mitoses in the hypo- 
basal portion before occurring in the epibasal portion, the basal cell 
evidently dividing first. It is quite common to find embryos of this 
stage with the apical cell yet undivided (figs. 14, 15). This cell 
also soon divides, either by a vertical wall or otherwise, as described 
later. A series of cross-sections of an embryo at this stage shows 
that the vertical walls do not usually lie in the same plane, but are 
inclined to one another at various angles (figs. 19-23). These verti- 
cal walls are usually perpendicular to the transverse ones, which, if 
obliquely inclined, usually result in oblique vertical walls, and the 
embryo may, in surface view of this and later stages, appear spiral. 
Occasionally some of the vertical walls are oblique to the transverse 
wall, even in the middle of the filament (figs. 17, 28). 
The first vertical walls are soon followed by a second series, usually 
at right angles to the first, typically dividing each segment into four 
cells (figs. 25, 26). These divisions may be more or less simultaneous 
(fig. 36), although not ordinarily so even in the same segment. 
