1897] THE LIFE HISTORY OF SAGITTARIA VARIABILIS 263 
does not agree with my own observations on the early develop- 
ment of the embryo of Alisma, where I found four cells pro- 
duced in acropetal succession before the longitudinal division of 
the terminal cell. I am inclined now to regard this as only an 
exceptional variation. However, such a variation may also 
occur in Sagittaria, since the succession of divisions of individual 
cells in an embryo does not seem to be so invariable as was 
once supposed. Sometimes as many as five cells in a single 
chain were observed without any indication of a longitudinal 
division in the terminal cell (fig. 52). In suchacase, of course, 
it is impossible to tell just how the various cells originated unless 
one is fortunate enough to find cases in which the nuclei are in 
the spindle stage. 
I do not consider it proper in this case to call the terminal 
cell, which gives rise to the cotyledon, the embryo cell, but 
shall call it what it really is, the cotyledon cell. Nor does it 
seem reasonable to include the middle cell in the suspensor. It 
will be seen that the development of the embryo proceeds 
gradually, and to call one cell a suspensor cell which at the next 
division becomes a cell of the embryo, is drawing an arbitrary 
line where none exists. The cell at the upper or micropylar 
end can be called properly a suspensor cell, since it never con- 
tributes to any part of the embryo proper, but is subsequently 
destroyed. The cells which finally become a permanent part of 
the Suspensor between the vesicular cell and the embryo are 
variable in number and are a late development. There is 
always, except in rare cases, at least one cell between the devel- 
oping embryo and the vesicular suspensor cell, which by basip- 
etal divisions contributes to the development of the root-tip, and © 
finally develops a filamentous suspensor, and this cell may be 
called a temporary suspensor cell. But it seems to me that in 
cases like Sagittaria the only reasonable terminology is to regard 
as embryo cells all those which go to make up the embryo, and © 
to restrict the term suspensor to that part —e never Jearniead : 
_ utes to the formation of the embryo. oo 
ake the usual course of events, the third division is. = 
