2 Mr. Grirrita on the Development of the Ovulum in Avicennia. 
The first change, subsequent to the application of the pollen-tubes to the 
apex of the sac, appeared to consist of the usual preparatory steps in the for- 
mation of cellular tissue (Tas. I. fig. 5.). 
The next change observed was one affecting the figure of the sac itself, 
which now exhibited, as it were, a short prolongation posteriorly in the direc- 
tion of the axis of the ovulum, and consequently in exact relation with the 
dense central tissue; or, in other words, instead of being straight, it now 
appeared curved at its anterior extremity. The subcylindrical body of the 
sac was also observed to have become prolonged posteriorly within the inner 
side of the ovulum (Tas. I. figs. 6, 7.). 
That half of the dilated head of the embryo-sac next the short central pro- 
longation was at this period observed to be filled with rudimentary cellular 
tissue or young albumen. As this albuminous tissue increases, it first occupies 
the whole of the original head of the sac, which then appears to become 
enlarged, and then to pass out of the apex of the ovulum (Tas. I. figs. 8, 9.), 
to which direction its subsequent enlargement is almost entirely confined. 
At the same time the posterior prolongation of the body of the sac continues. 
The albuminous tissue having attained some size, will be found to present 
towards its centre, and corresponding with the axis of the ovulum and that 
of the application of the pollen-tubes, the rudiments of the future embryo 
(Tas. I. fig. 9.). 
At a subsequent period the albuminous mass, being considerably increased 
in size, presented on its anterior surface a curved furrow or groove, which 
was found to correspond with the points of the cotyledons of the young em- 
bryo, now considerably increased in size (Tas. I. figs. 11, 19.).. At this 
period the part of the sac within the ovulum has undergone little change, 
except the posterior (lateral) prolongation, which has by.this time passed 
back into the placenta, within which it is divided in a di 
manner (Tas. I. fig. 10.). 
The next stage presented the points of the cotyledons quite naked (i. e. 
external to any part of the seed), they having protruded through the groove 
Thess mentioned. As the embryo increases in size. the cotyledons become 
more and more exposed: the part of the albumen below the line of exsertion 
of the cotyledons does not undergo much change; but that part above the 
gitate irregular 
