6 Mr. GnrrrrTB 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. 
Tae. 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, 
close to the apex of the ovulum, 
dense tissue (A. resinifera). 
Fig. 4. Embryo-sac of the same, separated, 
Fig. 5. Embryo-sac of an ovulum at the period atter 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 blac 
style, the fall of the corolla, and evident enlargement of the ovarium; part of a 
pallen-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, 
prolonged posteriorly, and also presents a short 
more advanced; the apex of the embryo-sac is 
and its body cylindrical, reaching to the central 
kening of the apex of the 
the ovulum ; i 
prp eet. e ovulum; the dilated apex has 
Fig. 8. Placenta and ovula (A. intermedia) 
aborted ; the fertilized one is 
its apex, 
at a more advanced stage: three of the ovula have 
seen laterally, and a protuberance (a) is visible from 
