OF SANTALUM ALBUM. 71 
conical, or rather spindle-shaped pillar, the free placenta of authors, arising from the 
centre of the base; the internal surface of the walls of the ovary are closely applied to 
the placenta, without however contracting any adherence either at the sides or above. 
In the youngest buds I examined (Tab. XVII. fig. 1) I found the central placenta with 
three cellular papillæ projecting downwards from the thickest portion, near the base, that 
part of the placenta below their origin being narrowed into a kind of peduncle (Tab. XVII. 
fig. 2). These papillæ, of cylindrical or slightly conical form, with blunt ends, pointed 
downward and a little outwards; they were composed of tolerably compact cellular tissue, 
and according to the view commonly taken of the structure of this genus, they are the 
nuclei of three ovules (fig. 2. a,a). In the youngest specimens examined, no trace of an 
embryo-sac could be seen, but a lighter streak (as seen by transmitted light) soon appears 
in the axis of each nucleus, indicating a cavity, and in a little farther advanced state a 
closed tubular process was found projecting from the point of each nucleus, the free 
extremity of a tubular embryo-sac extending internally up to the organic base of the 
nucleus. . Examined in successive stages, the tubular embryo-sac is seen to extend down- 
wards at first ; then its external (or anterior) end (organic summit) turns outwards, next 
suddenly upwards over the side of the nucleus; it becomes then more and more elongated 
until it has grown up upon the side of the placenta so far as nearly to reach its free sum- 
mit. It lies upon the outside of the placenta in the form of a slender filamentous tube 
(Tab. XVII. fig. 4, 5). At the same time the posterior or internal end of the tube elon- 
gates in the substance of the placenta until it makes its way nearly to the apex. These 
phænomena occur in all the other (occasionally four) ovules, alike. The tubular embryo- 
sacs contain protoplasmic matter with a few granules, but are comparatively clear as 
contrasted with the cells of the nucleus, which are filled with dense protoplasm and 
(starch-) granules. 
. The next stage is the formation of a bulbous enlargement of the embryo-sac at the 
point where it turns up to rise over the placenta (Tab. XVII. fig. 6). The free points of 
the tubular sacs also contract a slight adherence to the side of the placenta near the sum- 
mit, remaining free however in the greater part of their length, although closely applied 
to the side of the column. The protoplasmic pre ær to increase in quantity 
and consistence, especially at the apex and below the bulb. A septum is soon 
formed at the bot of the bulb, ital at first flat, becomes convex (looking upwards), 
and finally appears as an inner bulb projecting up into the cavity of the primary bulb 
(Tab. XVII. fig. 7). The septum divides the embryo-sac into two distinct portions ; I ar 
never discovered any cell-formation within the cavity behind (or below) the septum, either 
externally or internally to the nucleus. The only change this posterior (or oo cape Å 
inferior) part of the embryo-sac undergoes, is a tubular ramification in the su en 
the placenta, to be described presently. get n ae | 
About the time of the formation of the septum just nere - di ceva: 
period of the opening of the flower, the apex of the embryo-sae 
(clavate), and protoplasm accumulates on it. Soon after this, before any pollen-tubes 
i ular cell-nucleus, becoming gradually better 
reach the placenta, from the stigma, a granula of the clavate end, not quite at the extre- 
defined, makes its appearance in the protop 
