448 BOTANICAL GAZETTE [JUNE 
formation of the 3 transverse walls, vertical walls appear at right 
angles to each other in each horizontal tier (fig. 6), although the 
lowest cell may divide vertically before the appearance of the third 
transverse wall, as previously stated. These vertical divisions 
begin at the lower end of the embryo (fig. 5), a feature which is also 
noted by Woopsurn’s figures. Additional cross-walls then come 
in, and an embryo consisting of 5-7 tiers of cells is thereby formed 
(figs. 7,8). ‘This was a very common stage seen in the preparations. 
The additional transverse divisions occur chiefly in the upper part 
of theembryo. WoopsurNn has observed the occasional formation of 
Fics. g-11.—Older stages in embryogeny; 475. 
a triangular-shaped apical cell in the young embryo, and often 
of both triangular apical and basal cells. The writer has seen 
stages similar to those figured by Woopgurn, but found that the 
triangular form of the uppermost cell invariably resulted from an 
obliquely cut section. A truly median section has never revealed 
the presence of a triangular apical cell. 
With the definite establishment of the vertical walls in the 
embryo, both transverse and vertical divisions occur chiefly in its 
upper portion (fig. 7, 9, 10), and finally the sporogenous tissue is 
delimited from the amphithecium (fig. 11). Further development is 
typical of that of other Marchantiaceae which have beeninvestigated. 
