FERTILIZATION 
215 
the ovule m, in Fig. 165, reaches one of the cells shown 
at e, and transfers a generative cell into this egg-cell. 
latter is thus enabled to 
divide and grow rapidly 
into an embryo. ‘This 
the cell does by forming 
cell-walls and then in- 
creasing by continued 
subdivision, in much the 
same way in which the 
cells at the growing point 
near the tip of the root, 
or those of the cambium 
layer, subdivide.! 
227. Nature of the 
Fertilizing Process. 
The necessary feature of 
the process of fertiliza- 
tion is the union of the 
essential contents of two 
cells to form a new one, 
from which the future 
plant is to spring. This 
kind of union is found 
to occur in many cryp- 
togams (Chapters 
XX-XXIT), resulting 
in the production of 
a spore capable of grow- 
The 
WEES 
\ o He 
We 
FIG. 165. — Diagrammatic Representation of 
Fertilization of an Ovule. 
i, inner coating of ovule; 0, outer coating of 
ovule; p, pollen tube, proceeding from one 
of the pollen grains on the stigma; c, the 
place where the two coats of the ovule 
blend. (The kind of ovule here shown is 
inverted, its opening m being at the bottom, 
and the stalk f adhering along one side of 
the ovule.) ato e, embryo sac, full of pro- 
toplasm ; a, so-called antipodal cells of em- 
bryo sac; n, central nucleus of the embryo 
sac; e, nucleated cells, one of which, the 
egg-cell, receives the essential contents of 
the pollen tube; jf, funiculus or stalk of 
ovule; m, opening into the ovule. 
ing into a complete plant like that which produced it. 
1 See Kerner and Oliver’s Natural History of Plants, Vol. I, pp. 401-420. 
