214 BOTANICAL GAZETTE [SEPTEMBER 
cases he was able to determine the succession of walls in young 
embryos, which suggests the possibility that an apical cell may 
be found here. In Podocarpus Coxer (6) figures a number of 
embryo stages, some of which may have an apical cell; in others it 
appears doubtful. ARrNoxpr (1) and Lawson (22) show figures for 
the early embryos of Sequoia and Sciadopitys in which the embry- 
onal cell has formed 1 or more vertical walls, a condition which 
precludes the possibility of an apical cell, according to the views 
of some investigators. However, according to the later stages 
of Sequoia, figured by SHaw (37) and Arnotpr (1), an apical cell 
arrangement exists, and it is possible that the vertical walls were 
only the first obliquely placed walls of the apical cell, a condition 
which occurs occasionally in Pinus, and is explained in connection 
with figs. 13, 14, 15, and 21a. Saxton (34) shows some of the 
stages in Actinostrobus which are suggestive of an apical cell, and 
doubtless it may be found in many of the conifers. It is just as 
certain to be absent, even in some of the Abietineae, if STRAS- 
BURGER’S account of Picea (38) is correct, for if all 4 cells of the 
lower tier of the proembryo together produce an embryo, the apical 
cell loses its identity from the start. : 
It is evident that in Pinus a primitive condition is found, m 
which the apical cell is still functional for a considerable period, and 
that in some derived conifers this has been retained more or less, 
while in some evolutionary lines it has been suppressed or com- 
pletely eliminated. 
APICAL CELL IN RELATION TO PROEMBRYO.—One of the great 
difficulties in accepting the apical cell as having phylogenetic 
significance has been the impression that if such a stage may be 
found it does not exist from the start. In looking over the litera- 
ture it is apparent that many workers do not recognize an apical 
cell as such, unless it cuts off oblique segments from several 
cutting faces. Their apical cell would begin only with the first 
oblique wall. By studying the behavior of the segments in form- 
ing the suspensor the writer has shown that the embryonal cell 
is a hemispherical apical cell of a single cutting face, and that the 
primary suspensor cell is its first segment. We need not expect 
to go farther back in the proembryo than to when the embryo 
