164 BRITISH PLANTS 
the embryo-sac, discharges into it a nucleus, which fuses 
with the nucleus of the egg-cell. The egg-cell, thus fer- 
tilized, divides and develops into the new plant—the 
germ or embryo of the seed. The fusion of the male 
cell with the egg constitutes the act of fertilization, and 
by it the ovule becomes the seed. It is preceded by 
pollination—that is, by the transference of the pollen 
from the stamens in which it is formed to the stigmas. 
upon which it germinates. After fertilization, great 
changes take place in the ovules, a stream of food- 
material pours into them, and their coats become modified 
into protective envelopes for the seed. When these 
changes are completed, water is withdrawn and the seed 
passes into a resting or dormant state, from which 
it only emerges at germination. 
The success of the seed, from the biological point of 
view, is due to its efficiency in preserving the life of the 
embryo during periods inhospitable to growth, and to 
the ease and certainty of its dispersal by natural agencies. 
Pollination. 
The pollen which reaches the stigma comes either 
from the same or from another flower. In the former 
case the flower is said to be self-pollinated; in the 
latter, cross-pollinated. The terms “ self- ”’ and “ cross- 
fertilization ” are often used in the same sense. This 
is justified when pollination is followed by fertiliza- 
tion, but when we are only concerned with the means 
by which pollen is deposited on the stigma, and not what 
happens to it afterwards, it is better to use the term 
‘ pollination,” reserving “‘ fertilization’ for the act of 
sexual fusion itself. 
Self-Pollination (autogamy, Gr. autos, self ; gameo, I 
marry).—Autogamy is only possible when stamens and 
pistil are both present in the same flower. The seeds so 
produced give rise to offspring which more closely resemble 
the parent than plants produced by the co-operation of 
distinct parents. Self-fertilization is very common among 
plants, even among those which seem specially adapted 
for cross-pollination. On the publication of Charles Dar- 
win’s works on fertilization in flowers, people were so 
struck with the wonderful adaptations among flowers for 
