840 REPRODUCTION OF THE ANGIOSPERMIA. .- 
sac is, however, lable to many modifications ; thus, in some 
cases, as in the Orchidace, the embryo-sac completely oblite- 
rates the cells of the nucellus by its development, so that the 
ovule consists simply of it and its two proper coats. In the 
Fie. 1164. Fic, 1165. Fic. 1166, 
Fig. 1164, Vertical section of the orthotropous ovule of a species of Poly- 
gonum. ch. Chalaza, n. Nucellus invested by two coats. m. Micropyle. 
s. Embryo-sac. c. Germinal vesicle or corpuscle-——Fig. 1165. The 
ovule, some time before fertilisation. a. The outer coat. b. The inner 
coat. s. The embryo-sac, with three nuclei at the upper end, Fig. 
1166. The internal parts of the ovu'e a short time before fertilisation. 
a. Inner coat of the ovule. s. Embryo-sac. 06, Germinal] vesivies. c. 
One of the antipodal cells. (After Hofmeister.) 
Leguminose, the embryo-sac increases still further, and causes 
the absorption of the secundine or inner coat of the ovule also, 
so that it is then simply invested by one coat ; while in other 
plants, as in the Santalaceze, the sac elongates 
Fic. 1167. so much at the apex as to project out of the 
micropyle. The embryo-sac contains at first 
a more or less abundant quantity of proto- 
plasm ; in this afterwards appear nuclei (jig. 
1165, s), which, surrounded by masses of 
naked protoplasm, form a corresponding 
number of cells (usually three) which are 
commonly termed germinal vesicles (fig. 
1166, b). The vesicles are situated at or 
near the summit of the embryo-sac, one of 
them being the vosphere (fig. 1167, e), which 
after fertilisation is sometimes called the 
x vosperm, and ultimately becomes the embryo. 
Aig. V167. | Polygonum ~The two remaining cells after disappearin, 
divaricatum. Mature 5 PP s 
germinal apparatusin reappear, and are called synergide ( fig. 1167, 
apex of embryo-sac, s 5) At the base of the embryo-sae, as 
with two synergide, ~? : : 
s,s, and the oosphere,e, already described (page 328), there are also, 
before fertilisation, two or more nucleated 
primordial cells, termed antipodal cells (fig. 1166, c). 
Such is the general structure of the ovule before it is 
fertilised, upon which so much difference of opinion, until the 
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