Oross-ft ftiliscLti o tt of Cereal*. 
689 
seeds capable of germination may be appreciated by a glance 
at the following table. 
Seeds fertile. 
Self-fertilisation 
Cross-fertilisation 
I 
4. 
Pollen of the same flower. 
Pollen from another flower of the same plant. 
Pollen from the flower of a similar plant of 
the same species. 
Pollen from the flower of a dissimilar plant 
of the same species, that is a variety. 
Seeds of the hybrid almost invariably infertile. 
Hybridisation . 
/5. Pollen from the flower of a different but 
closely related species of the same genus. 
I 6. Pollen from the flower of a remotely related 
species of the same genus. 
7. Pollen from the flower of a species of an- 
other hut nearly related genus. 
The best results are obtained from fertilisation by pollen 
taken from another individual of the same species, whether that 
has the same characters as the female plant (3) or differs from 
it to such an extent by characters transmitted from generation 
to generation as to be recognised as a distinct variety (4). An 
improvement may be detected by using the pollen from another 
flower of the same plant (2) over those that are fertilised by the 
pollen from the same flower (1). Fertile seeds are produced, 
generation after generation, fertilised in any of these methods. 
In the case of hybrid plants it is very different. When the 
pollen is taken from an allied species of the same genus (5), it is 
easy to secure fertilisation and to obtain perfect seeds that will 
germinate. But the hybrid plant in the next generation rarely 
produces fertile seeds. The plants themselves usually present 
vigorous vegetative characteristics — a taller straw and larger 
leaf — but the sexual organs are weak. The stamens may look 
perfect, but the pollen grains do not ripen and the anther cells 
do not open. The ovules, too, are incapable of fertilisation. 
Should ripe pollen grains get access to the stigma and penetrate 
to the ovule, they may excite some activity and lead to the 
growth of the ovule, but without resulting in the formation of 
an embryo plant ; or an embryo may be formed which, however, 
is incapable of germination when the seed is ripe ; or even the 
further stage may be reached and some of the ovules may develop 
into perfect seeds capable of germination. 
To the nurseryman who seeks only to obtain fine flowers the 
production of barren hybrids is no disadvantage. From a num- 
ber of seeds thus produced he obtains a considerable variety of 
plants, and those that possess any striking peculiarity in the 
VOL. IV. T. S. — 1G Z 3 
