1897] THE LIFE HISTORY OF SALIX 159 
my preparations afforded is shown in fig. go. As the pollen tube 
enters the sac the synergids usually break down, and even their 
nuclei disappear. A sac immediately after fertilization is shown 
in fig. 32, in which the oospore is much enlarged and is forming 
a cellulose wall, and only a nearly disintegrated nucleus and a 
mass of protoplasm mark the remains of the synergids. The 
primary endosperm nucleus has not yet divided. A typical case 
is shown in fig. 36, which represents the pollen tube entering 
between the beaks of the synergids. The fusion of sex cells has 
probably not taken place, for no membrane has yet formed around 
the oosphere. The primary endosperm nucleus has increased 
greatly in size, but has not divided. The enlargement of the 
endosperm nucleus before fertilization is also shown in fig. 34. 
A somewhat later stage is given in fg. 39. The pollen tube can 
be seen still between the beaks of the synergids. The oospore 
has its cellulose wall, but the primary endosperm nucleus, 
although greatly enlarged as usual, has not yet divided, this 
enlargement beginning before the pollen tube reaches the beaks 
of the synergids. 
A very peculiar case is represented in fig. 38, in which the 
embryo is quite advanced, but both synergids still persist. These 
Synergids are plump and have definite cell walls, but have no 
vacuoles, and their nuclei are at the lower end instead of the 
upper where they are usually situated. The pollen tube, of 
course, is not the one which assisted in fertilization. A similar 
Condition is shown in fig. 75, but here the synergids have no 
walls, and the pollen tube has collapsed. These cases indicate 
that fertilization may take place without the assistance of the 
Synergids. Another singular case is furnished by fg. 37, in 
which the embryo is quite advanced, but the primary endosperm 
nucleus, although it has grown very large, has not yet divided. 
As a tule, the division of the primary endosperm nucleus 
precedes the division of the oospore, and for a short time the 
nuclei of the endosperm multiply more rapidly than = cells of 
the embryo. A two-celled embryo is usually correlated beta 
_ four nuclei in the endosperm, a four-celled embryo with eight or 
