BRIEFER ARTICLES. 
Development of the embryo-sac of Jeffersonia diphylla. (WiTH 
PLATE XXvill.)—/effersonia diphylla Pers. is a very favorable plant in 
which to study certain phases of embryology. This is due partly to 
its large cells and nuclei, and partly to the fact that its embryonic 
tissues are very readily stained and sectioned. Several stains were 
used, such as haematoxylin, fuchsin, and alum cochineal, with fair 
success, but for staining zw Zofo alum cochineal proved most satisfac- 
tory. The sections were counter-stained on the slide with Bismarck- 
brown. 
The mother-cell of the embryo-sac arises as an hypodermal cell at 
the apex of the nucellus. It contains but one nucleus and always 
Stands with its long axis parallel to that of the nucellus (fig. 1). No 
tapetal cell is formed in this plant. In an ovule that has advanced 
somewhat in development we find that this mother-cell is preparing 
to divide into two similar cells by a transverse wall (figs. 2 and 4). 
This is indicated by the dividing nucleus (fig. 2). 
In the next step toward maturity, it is noticed that the two cells 
just formed repeat in every detail (fig. 5) the process just described; 
so that there are now four cells resulting from two successive divisions 
of the mother-cell (fig. 6). Occasionally the uppermost of these four 
cells divides into two by an almost vertical wall (fig. 7). The transverse 
walls separating these four cells are somewhat swollen, and more dis- 
tinct than the others (fig. 6). By repeated periclinal divisions of the 
epidermis of the nucellus, the row of four daughter cells is soon cov- 
ered at its summit by four or more layers of cells (fig. 6). The num- 
ber of these layers seems to increase quite uniformly with the age of 
the nucellus, though some exceptions were noted (figs 4, 5, 6). 
In figure three (3) are shown two cells, the upper of which is much 
the larger. From my own observations it does not seem probable 
that the lower cell has arisen by division from the upper one, but that 
it is merely a cell of the axial row which did not divide but merely 
increased in size. 
Of these four cells, which by successive divisions have arisen from 
the mother-cell, the lower one undergoes further development and 
becomes the embryo-sac. This cell increases in size at the expense of 
the three cells above it, together with the adjacent cells of the nucel- 
lus (fig. 10). The upper three cells are first absorbed and their cavi- 
ties become almost obliterated by the surrounding turgid cells of the 
[423] 
