1892.] Briefer Articles. 259 
for in every representative of both groups, as far as is known to the 
writer, there is to be found the typical seven-celled embryo-sac, and it 
is hardly possible that such a structure could have arisen independently 
in both groups. If in any representative of either of these two groups 
of plants an embryo-sac should be found varying considerably, or even 
a little from the type, something toward a solution of the problem 
would at least be suggested. . It is perhaps, among the lower forms 
that we are to seek such variations, if there are any. With this in view 
work was begun upon the development of the embryo-sac in Ariseema 
triphyllum. Although no variation from the common type in the 
structure of the mature embryo-sac was found, yet a few details in the 
process of development from the initial cell seem worth mentioning 
The initial cell (mother cell) of the embryo-sac arises as a single 
hypodermal cell in the apex of the nucellus (figs. 1, 1a). This cell is 
well defined as soon as the first traces of the inner integument of 
the ovule is perceptible, or even sooner. All the cells now increase 
in size, and those of the epidermis divide by periclinal walls (fig. 2). 
The initial cell next divides by longitudinal walls into three or four 
cells two of which may be seen in longitudinal section (fig. 3). A trans- 
verse section at this stage of development shows four cells («) which in 
all probability were derived from the initial cell. As tar as is known 
to the writer, the longitudinal division of the initial cell of the em- 
bryo-sac has been observed and recorded only by Strasburger." This 
author calls attention to a very unusual state of things in Rosa livida, 
where about four cells of similar size may be seen in longitudinal 
section.? He also states that he has seen two cells in longitudinal 
Section, but he does not say in what plant or plants it was observed. One 
of these cells now enlarges considerably (fig. 5), and divides by a cross 
wall into two cells (fig. 6), the lower one being usually larger than the up- 
Per. The lower now absorbs the upper (fig. 7), and develops in the 
usual manner into the embryo-sac (fig. 11). (The intervening steps in the 
Process are omitted here since they correspond to those of the type.) In 
; in all other cases it was always of a more delicate structure, but not 
‘ppreciably swollen. One instance was observed where there was no 
Jarge nucleus 
in in 
€ach end and each nucleus accompanied by a V uole as $ det 
8. 66. is, however, must be of very rare occurrence, for in 
t in the de- 
Ks ; 
oe Angiospermen und die Gymnospermen, p. 14- 1879. 
“©. p. 14, taf. iv, fig. 50. 
