116 BOTANICAL GAZETTE [ FEBRUARY 
divisions of a two-sided apical cell, and from these early seg- 
ments a pedicel is formed. From the cells supported by the 
pedicels arise the sterile external wall of the gametangium, and 
the fertile gamete mother-cell tissue inclosed by the wall. Both 
organs are closed while developing, but organize special regions 
in which apertures appear at maturity. 
2. Lhe homology of the axial row series —That the cells com- 
posing the axial row constitute a homologous series is indicated 
by development of the row. In the first place, egg, ventral 
canal cell, and neck canal cells are all closely related in origin. 
They are all the progeny of either a single cell cut from the 
truncate apex of the terminal cell (Riccia), or of such a cell and 
subsequent cells cut from the same region in identically the same 
way as the first (Musci). Again, egg and ventral canal cell are 
sister cells, and at the time of formation are not widely different 
in size or appearance (jigs. 26, 28, 29). It appears possible even 
that the ventral canal cell or the lowest canal cell may function 
as the egg. 
The theory that the ventral canal cell is an abortive egg is 
strongly supported by Chamberlain’s account of Pinus (17), in 
which the ventral canal cell is occasionally organized as an egg 
and in rare cases may function as such. Ikeno (19) from a 
study of Ginkgo, and Land (21) from his study of Thuja have 
arrived at similar conclusions, Gayet (15) reports an instance 
in Marchantia where the ventral canal cell was fertilized instead 
of the egg, but unfortunately the specimen was not saved, 
nor was a figure made. My own observations on Mnium 
yielded a case in which the ventral canal cell had outstripped the 
egg in growth (fig. 42), and doubtless would have been fertilized 
in place of the egg. It is possible in cases of this nature (fig. 42) 
that the larger of the two cells may be the lowest cell of the 
canal row and would later have given rise to a ventral canal cell 
and an egg. 
Another unusual case which supports this homology is seen 
jig. 43. UHere there are two eggs each with its own ventral 
canal cell. There can hardly be any doubt that either or both 
of these eggs could have functioned and produced embryos, had 
in 
