OF SANTALUM ALBUM. 73 
determine its conversion into a cell. The nucleus becomes perfectly defined, as separate 
from the surrounding protoplasm, just at the period of fertilization. At the same time 
this surrounding protoplasm (contained in a * primordial utricle * lining the entire embryo- 
sac, down to the septum of the bulb (Tab. XVII. fig. 6)), becomes more dense and granular, 
sometimes exhibiting largish starch-granules. 
Little further change occurs at the apex of the embyro-sac for some time; merely the 
cell-membrane enclosing the nucleus becomes thicker, and the cells assume å more elliptical 
form. The next step is the formation of endosperm-cells from the protoplasm of the 
embryo-sac. This takes place by segmentation, or free cell-formation from the whole 
abundant mucilaginous protoplasm, commencing always in the bulb, often advancing 
from them before it proceeds up the tubular part of the embryo-sac, which at first presents 
only a single row of ‘primordial utricles’ (Tab. XVII. fig. 12); the latter then divide 
perpendicularly (Tab. XVII. fig. 13), and the cells produced, appear to apply themselves 
to the side-walls and multiply for some time by free cell-formation in the centre 
(Tab. XVII. fig.15). Ultimately cell-division occurs, and the whole cavity of the swollen 
embryo-sac being filled up with cellular tissue analogous in character to that of the 
nucleus,—namely, composed of squarish cells with thin walls, filled with dense protoplasm, 
containing increasing quantities of minute starch-granules,—the albumen of the end 
becomes a distinct structure, on the surface of which all trace of the originally bounding 
embryo-sac is soon lost (Tab. XVII. fig. 16). 
The first change in the germinal vesicle is its elongation downwards into a cylindrical 
form; then cross septa appear (Tab. XVII. fig. 15 g, Tab. XVIII. fig. 19 g) one after an- 
other, so that it is converted into a short row of cells. The uppermost remains appressed 
to the coagula in the apex of the embryo-sac, and does not appear to become developed 
further ; forming a kind of suspensor. The lower cells multiply greatly (Tab. XV ITI. fig. 23) 
and form an elongated, clavate cellular body, the embryo, in which at first no trace of 
regions can be detected,—only a greater density of the tissue and abundance of granular 
contents at the cotyledonary (inferior) extremity (Tab. XVIII. figs. 22 & 24 g, fig. 25). 
The conditions of the walls of the ovary during these changes deserve some attention; 
the outer substance of the young fruit is formed of a firm layer of tolerably equal thick- 
ness all over, constituting what we may call the epicarp together with the mesocarp 
(Tab, XVIII. figs. 27 & 288). These define and correspond to the outward form of ". 
fruit. The portion immediately beneath the epidermis is composed of oblong d pe 
their longest dimension in the direction of the axis of the fruit; these pass insensibly In 
a denser layer of closely-packed polygonal cells with thick walls. These ea pen ires 
coloured, while the endocarp is nearly colourless (Tab. XVIII. figs. 27 = ) sone 
of the mesocarp (well defined internally to the naked eye) appear, under the microscope, 
å å nice .27 & 28 r), composed of membranous, 
to pass again insensibly into the soft endocarp pico je hate ihe siget; 
globular, and polygonal cells, loosely packed, of m 
than those of the mesocarp. The endocarp (figs. 27 & 287) - veste et 
the dark rind of the fruit (s) and the placenta (and ovules) (0, p), å Å li, i6 is of 
expansion of the ovary. Where in contact with the 2... se. dee A perpendi- 
denser texture and of darker colour, having a definite, separa i i 
VOL, XXII. 
