of Hippuris vulgaris. 261 
From the fact that the embryo-vesicle is developed at so long 
a period before the bursting of the anther, little doubt can remain 
as to its existing prior to the act of impregnation, and not being, 
as supposed by Mirbel and Spach, a consequence of that act. 
Still less can it be supposed to be the end of the pollen-tube, ac- 
cording to the theory of Schleiden and his followers. 
We now proceed to notice the changes which the embryo- 
vesicle undergoes subsequently to the act of impregnation. After 
impregnation, the granular protoplasm, which has accumulated 
at the larger extremity of the embryo-vesicle, becomes trans- 
formed into a spheroidal cell. A septum is then observable at 
the lower part, crossing it horizontally, by which it is divided 
into two cells. Of these the inferior is developed downwards by 
successive merismatic division, so as to form a confervoid fila- 
ment, the suspensor. The upper assumes at the same time a 
spheroidal form, and is distinguished from the rest by being 
filled with granules, exactly as occurs in the Orchidacee. Soon 
after it divides by a longitudinal septum, and subsequently by a 
transverse. These are followed by successive divisions, and the 
embryo with its suspensor is formed. While these changes are 
taking place, the embryo-vesicle, which in the early stage is ad- 
herent by one of its extremities to the micropyle-end of the em- 
bryo-sac, becomes correspondingly enlarged and elongated. It 
however never becomes completely filled with the cells of the 
suspensor, or at least not until a very late period. It seems to 
be narrowed at its apex, either by the absorption of its contents 
by the developing embryo, or by the pressure of the contiguous 
parts. Subsequently the round mass of cells described above, 
to which the term embryo-globule has been applied, undergoes 
further development, and the cotyledons and other parts being 
gradually formed, the embryo assumes its characteristic appear- 
ance. 
Thus we see in this plant—1st. That the embryo-vesicle exists 
at a period previous to the act of impregnation ; 2nd. That after 
impregnation a number of cells are formed by an endogenous 
process in its cavity which assume a confervoid arrangement ; 
ord. That of these one is selected to be developed into the em- 
bryo; 4th. That the rest undergo no further development, but seem 
to conduce to the nutrition of the embryo. These facts are in every 
respect conformable to what is known of the embryogenic pro- 
cess in the Orchidacea, Onagracee, Scrophulariacee, Crucifere, 
and other natural orders. 
Since the above observations were made, I have had the oppor- 
tunity of seeing the results of two very important series of re- 
searches by Hofmeister of Leipzig and Tulasne. These researches 
lead to the conclusion, that the mode of development above de- 
