THE DEVELOPMENT OF THE EMBRYO-SAC IN 
SOME MONOCOTYLEDONOUS PLANTS. 
a KARL M. WIEGAND. 
(WITH PLATES VI AND VII) 
THE material for the following study was prepared in the 
ordinary way, by fixing in the chrom-aceto-osmic acid solution, 
imbedding in paraffin, and staining with the gentian-violet-orange | 
combination. Although the development in Canna was found 
to be nearly normal, that in each of the other two plants showed 
some very interesting and important variations. Whether these 
throw any light on the problem of the homology of the embryo- 
sac can be determined only by more extended study of other 
plants. 
Convallaria majalis L. 
THE HYPODERMAL CELL AND ARCHESPORIUM. 
The embryo-sac of Convallaria is derived from a hypodermal 
cell situated at the apex of the nucellus. This hypodermal cell 
is first discernible as an enlarged oblong or more or less distinctly 
triangular cell at the apex of the nucellus and directly under- 
neath the epidermis; but can also be distinguished from the 
adjacent cells by its larger size and more granular contents. 
Very early in its development a single cell, the so-called “tape- 
tum,” is cut off on the side adjacent to the epidermis. This 
immediately divides by an anticlinal wall into two daughter cells 
which lie side by side at the summit of the embryo-sac (jig. 7). 
The nucellus is comparatively broad, and the growth of the 
archesporium taking place subsequent to the separation of 
the wall-cell is to a large extent ina lateral direction. To 
accommodate themselves to this the two daughter wall-cells 
undergo repeated anticlinal division, so that eight or ten cells 
are formed, all arranged in the same plane, and forming a plate 
of tissue just beneath the epidermis (fig. 2). The nuclei of 
1900] 25 
