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



have been, partly at least, derived, suffering no change in direction whatever, 

 and the other, from which the albuminous covering might have equally resulted, 

 only a partial one. The embryo also, in its earlier stages of development, un- 

 dergoes a degree of change of direction, but only sufficient to enable it to pass 

 up outside the ovulum, in the same direction it would have maintained had it 

 been ordinarily developed. 



EXPLANATION OF THE PLATE. 

 Tab. I. 



Avicennia resinifera, Forst. fide Jack, and Av. intermedia, GrifF. MSS.* 



Fig. 1. Placenta and ovula, at an early period before expansion of flower, and before the 



corolla exceeds the calyx in length (species not noted). 

 Fig. 2. Longitudinal section of one of the ovula of the same ; the subsequent dense central 



tissue appears to be commenced. 

 Fig. 3. Longitudinal section of an ovulum, more advanced ; the apex of the embryo-sac is 



close to the apex of the ovulum, and its body cylindrical, reaching to the central 



dense tissue {A. resinifera). 

 Fig. 4. Embryo-sac of the same, separated. 

 Fig. 5. Embryo-sac of an ovulum at the period alter the application of the pollen-tubes to 



its apex: — magnified about 500 times {A. resinifera). 

 Fig. 6. Longitudinal section of an ovulum of the same after blackening of the apex of the 



style, the fall of the corolla, and evident enlargement of the ovarium ; part of a 



pollen-tube is seen attached. The embryo-sac is enlarged, and extends further 



posteriorly ; otherwise there is little change in the ovulum. 

 Fig. 7« Longitudinal section of an ovulum, a little more advanced. The embryo-sac is more 



prolonged posteriorly, and also presents a short prolongation corresponding with 



the axis of the ovulum. It is still interior to the ovulum ; the dilated apex has 



commenced to be cellular. 

 Fig. 8. Placenta and ovula {A. intermedia) at a more advanced stage : three of the ovula have 



aborted ; the fertilized one is seen laterally, and a protuberance (a) is visible from 



its apex. 



* A. intermedia is founded on a Malacca plant altogether intermediate between what appears to be 

 A. tomentosa and A. resinifera. 



