158 Bliss.— A Contj'ibution to the Life-history of Viola. 
mother-cell has increased to several times its original size, and occupies 
a central position in the nucellus. Its cytoplasm is very scanty, except in 
the region of the spindle. In some cases the macrospore-mother-cell has 
elongated to twice its width at the metaphase of the first division, but often 
the cell is still spherical as in the early prophase of division (Fig. 4). 
At the close of the first division a distinct cell-wall is laid down, giving 
rise to two cells of nearly equal size (Fig. 5). Each of these two cells 
divides, and the result is an axial row of four cells. The development of 
the axial row in Viola differs from that described for Trillium by Coulter 
and Chamberlain (2), for Houstonia by Lloyd (6), for Larix by Juel ( 5 ), and 
for the great majority of Angiosperms as described by other writers, in that 
the upper daughter-cell, the one nearest the micropyle, divides first. 
The cells of the axial row in Viola are not always arranged in a vertical 
row as represented in Fig. 6, but the walls may be laid down obliquely 
(Fig. 8), resulting in a group of cells in which the arrangement of the macro- 
spores more nearly approaches the tetrad arrangement characteristic of 
typical spore formation. In this respect, the arrangement of the cells in 
the axial row in Viola corresponds to the arrangement figured for Delphinium 
(Mottier, 7 ), and for Fatsia japonica (Ducamp, 3 ). In Viola y generally the 
lower megaspore, the one furthest removed from the micropyle, is the 
functional megaspore, and develops into the embryo-sac. This order of 
development, however, was not invariable. Cases were observed in which 
the third megaspore became the functional megaspore (PI. XVIII, Fig. 10), 
and still others in which, although the second and third cells increased equally 
in size for some time, the second without doubt was to develop into the 
embryo-sac. That the other cells of the axial row are disentegrating at 
this time is evidenced by the densely staining irregular masses of cytoplasm 
(Fig. 11). 
Development of the Female Gametophyte. 
During the rapid growth of the functional megaspore, the dense 
cytoplasm of its early development becomes vacuolate. Preparatory to its 
germination the nucleus moves from a central position in the cell to the 
micropylar end. At this stage, the mother-cell of the embryo-sac extends 
nearly one-third the length of the nucellus. The changes subsequent to the 
formation of the axial row take place rapidly, the integuments very soon 
extend to the top of the nucellus, and in Fig. 12 are just beginning to curve, 
preparatory to enclosing it. In the two- celled embryo-sac shown in Fig. 12 A, 
the nucleus has divided and the two daughter nuclei have separated, one 
nucleus remaining at the micropylar end of the sac, while the other has 
passed to the extreme opposite pole. The two nuclei are connected by 
strands of cytoplasm, and there is a slight condensation of cytoplasm at 
both poles and at the periphery of the embryo-sac. In the central portion 
