Mr. Griffith on the Development of the Ovulum in Avicennia. 3 



same line, or rather between the inner cotyledon and body of the ovulum, 

 becomes enlarged and flattened almost into a membrane ; and even when the 

 cotyledons are as long as the placenta, this part of the albuminous tissue 

 equals them in length (Tab. I. fig. 13.).-; ^J^\^ -i 



The mature embryo, with the exception of its radicle, which is always im- 

 bedded in the albuminous tissue, may be said to be naked. The upper part 

 of the albumen at this period is much dilated, and almost membranous ; the 

 edges are very irregular (Tab. I. figs. 13 & 14.). 



l^he conduplication of the cotyledons takes place at an early period ; their 

 inequality at a much earlier, even before the protrusion of their points. 



The central prolongation of the sac was not observed later than the period 

 represented by fig. 12. Tab. I., but it is probable from appearances that it is 

 at length filled with albuminous tissue. 



The exact distance to which the vascular fascicle at length reaches was not 

 observed : probably it extends, when complete, to the apex of the short central 

 prolongation of the sac. 



The above observations were made very shortly before my departure from 

 Malacca : they are deficient in several respects ; but of the mode by which the 

 embryo becomes external to the seed to so great a degree I can speak with 

 the requisite confidence. \ r-^« ''•. - ",■ 



I novi^ proceed to offer my remarks on the circumstances detailed above. 



The elongation of the posterior end of the embryo-sac, occurring as it does 

 in a plant so different in general organization from those in which it has 

 hitherto been observed, appears to me remarkable. It is curious that this 

 prolongation has only been observed in association with a particular form of 

 the free central placenta, and thus the exact observation of the corresponding 

 developments in Olax and Congea becomes more desirable than ever. 



The shape of the embryo-sac in that stage, represented by fig. 7- Tab. I., 

 is also worthy of notice : so far as I know, it is the only instance of an 

 embryo-sac prolonged posteriorly, it may be said, from two points of its 

 surface, or which may not be considered to be in itself a rectilinear body. 

 The general analogy of the relations of the embryo-sac with the nucleus would 

 lead me to suppose that the embryo-sac of Avicennia consisted originally of 

 that part in the axis of the ovulum, viz. the head or dilated end, and what I 



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