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growth very rapid. Then, however, it expands rapidly, its 
growth in length being considerably greater than that in 
breadth. The embryo-sac, at the time indicated by figure gg, 
occupies the center of the upper half of the nucellus, the 
cells immediately surrounding it appearing somewhat crowded 
or compressed. After fertilization, however, this tissue at 
once gives way before the expanding endosperm. The tissue 
surrounding the embryo-sac now colors a little more deeply 
when the preparation is stained. While growth in length 
is proceeding rapidly the nucellus becomes cleft from apex 
to chalaza, though apparently due to the tension of growth 
in its peripheral region and not to any influence of the 
endosperm. 
The endosperm, after fertilization of the odsphere, soon be- 
comes distributed peripherally (fg. 50), and forms an ex- 
ceedingly thin layer for some time. The starch may still be 
found in simple and compound grains distributed irregularly 
in this layer of protoplasm. During this period the nuclei 
increase considerably in size, as can be seen by a comparison 
of figures 4g and 50, which were drawn to the same scale. 
At this time the endosperm is non-cellular, but the nuclei 
soon become separated by walls throughout, and in its upper 
portion it appears as shown in figure 57, at which stage all 
traces of starch have disappeared. The cells of the endo- 
sperm are most compact in its outer portion, those more cen- 
trally situated possessing only a thin layer of cytoplasm 
which lines the cell-wall. 
Only two conditions of the embryo were observed in Bry- 
onopsis. After fertilization the odsphere enlarges to a consid- 
erable degree before dividing (fg. 50). The earlier cleavages 
were not discovered in any of the preparations, but a later con- 
dition (fig. 57) was found which shows the embryo to be at 
one stage almost spherical in form with no visible suspensor. 
No differentiation of structure is apparent at this stage except 
the epidermis. From this condition it may be inferred that 
the differentiation of form and structure proceeds in this form 
about as in some of the other types described. In view of 
