2 Mr. Griffith on the Development of the Ovitlum 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 (Tab. 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 (Tab. 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 (Tab. 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 

 (Tab. 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 (Tab. I. figs. 11, 12.). 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 digitate irregular 

 manner (Tab. I. fig. 10.). 



The next stage presented the points of the cotyledons quite naked (/. e. 



external to any part of the seed), they having protruded through the groove 



above 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 



