306 



FERTILIZATION. 



opposed to the pre-existencc) It is a small mass or globule of pro- 

 toplasmic matter, either loose in the cavity of the embryo-sac near 

 the place to which the pollen-tube is applied externally, or else ad- 

 herent to the interior surface of the wall of the embryo-sac in this 

 immediate vicinity, or sometimes separated from the embryo-sac by 

 an interposed globule, or by a pair of such globules. This body, the 

 rudiment of the future embryo, has been termed the embryonal or 

 germinal vesicle. This is not yet a 

 cell ; for it has no covering or wall 

 of cellulose. But it soon becomes 

 one when a pollen-tube reaches the 

 embryo-sac, the first known result of 

 fertilization being that a coat of cel- 

 lulose is deposited upon its surface. 

 This newly-formed cell grows by 

 cell-multiplication (33), either pro- 

 ducing a mass of cells, as shown in 

 Fig. 10-14, or else in the first place 

 developing into an elongated cell or 

 a thread-shaped chain of cells (the 

 suspenior), the lower cell of which 

 divides in all directions, forming a 

 mass, which as it grows shapes itself 

 into the embryo (Fig. 549-553). 

 The radicle or root-end of the em- 

 bryo is always that by which it is 

 attached to the suspensor (which 

 ordinarily soon disappears) or to the 

 summit of the embryo-sac, the coty- 

 ledons occupying the opposite ex- 

 tremity. The radicle accordingly 

 is always directed to the orittce or 

 micropyle of the ovule and seed. 

 580. Through the fertilization of as many germinal vesicles, two 

 or more embryos are frequently found in the same seed, in the 

 Orange, the Onion, and many other plants. There are generally 



FIG 548 Magnified pistil of Buckwheat; the ovary and ovule divided lengthwise: some 

 pollen on the stigmas, one grain distinctly showing its tube, which has penetrated the. st) 1b, 

 reappeared in the cavity of the ovary, entered the mouth of the orthotropous ovule (o), and 

 reached the cmbr^o-sac (s) near the embryonal vesicle (e). 



