~ 
REPRODUCTION OF THE ANGIOSPERMIA. §39 
take place in this latter are, according to Strasburger, these :— 
disappearance of the original nucleus, and formation of four to 
eight new nuclei by condensation of the protoplasm and subse- 
quent secretion of a cellulose wall around them. In this way 
four to eight new cells are formed by division of the central cell 
after fertilisation ; these new cells divide so as to form cellular 
filaments, which break out through the bottom of the endosperm 
into the substance of the nucleus (jig. 1162, c). At the ends of 
these filaments cell-division again occurs (fig. 1162, p); and from 
the apex of one of these suspensors or pro-embryos is developed 
by repeated cell-division in various directions, the embryo 
(D, em). At one stage (in Thuja) a single apical cell, the 
terminal one of a group of five, from which ultimately all the 
tissues of the embryo are formed, recalls the single apical cell of 
the Cryptogamia, but it is soon lost by subdivision. As there 
are several corpuscles, and each produces four suspensors, a 
large number of rudimentary embryos are developed ;_ but 
usually only one of all these rudiments is perfected. 
‘That embryo which is fully developed gradually increases 
im size, and most of the structures above described disappear, so 
that the ripe seed exhibits a single embryo embedded in a mass 
of endosperm, the latter originating apparently from the nucleus 
of the ovule. The radicle is covered by a pileorhiza, which is 
ultimately blended with the substance of the endosperm.’ 
B. Reproduction of the Angiospermia.—The structure of the 
pollen-cells of the Angiospermia has been F 
already described (see Pollen, and page 836), Fie 1163. 
and need not be further alluded to in this place. 
The ovule has also been particularly noticed, 
and we shall now only recapitulate its com- 
ponent parts at the time when the pollen is 
discharged from the anthers—that is, just be- 
fore impregnation takes place. It then consists 
of a cellular nucellus, containing one large cell, 
the embryo-sac, which is the mother-cell of the 
oosphere (figs. 1163, b, and 1164, 1), enclosed 
generally in two coats—an outer or primine 
( fig. 1163, d), and an inner or secundine, ¢. But Fig. 1163. Vertical 
sometimes there is but one coat (jig. 740, s), eee pe ownle 
a a diagrammatic). a. 
and in rare cases the nucellus is naked or Nucellus. 5. Em. 
devoid of any coat (fig. 738). Deer & Inner 
These coats completely invest the nucellus [°Mieropyie. 7.Cho, 
except at the apex, where a small opening laza. g. Funiculus. 
or canal is left, termed the micropyle (jigs. 
1163, e, and 1164, m), that portion of it which passes through 
the primine being sometimes spoken of as the exostome, and 
the part going through the secundine as the endostome. In 
the interior of the nucellus, but of various sizes in proportion 
to it, the embryo-sac (jigs. 1163, b, and 1164, s) is seen. The 
