Hayes and Garber - Cucurbit Breeding

MODE OF REPRODUCTION IN RELATION TO BREEDING 35
feathery stigma and of three stamens with anthers, all of which
are enclosed by the lemma and palea. Opposite the base of the
palea are two tiny sac-like organs, lodicules. The increase in size
of these organs due to water absorption causes the flower to open.
This occurs when the stigma is receptive and at this time the
elongation of the filaments causes the
anthers to protrude from the glumes,
when they promptly dehisce. The
process of blooming is very rapid and
seldom requires more than 20
minutes. Leighty and Hutcheson
(1919) state that the opening of the
glumes from beginning to completion
may not require more than one
minute, that the anthers may be extruded
and emptied of their contents
within two to three minutes and the
glumes again become tightly closed
at the end of 15 to 20 minutes.
Kirchner (1886) states that about
one-third of the pollen falls inside
the flower. As the pollen is blown
around the field by the wind it is
easily seen that natural crossing
may sometimes occur.
Investigators
differ in their beliefs
regarding natural crossing in
small grains. De Vries (1906)
says " wheat, barley and oats are
self-fertile and do not mix in the
field through cross-pollination . ' '
Biffin (1905) states that he has never
observed a case of
cross-pollination
in wheat; while Fruwirth (1909) lists
several German breeders who have
given instances of natural crosses.
Fruwirth says
" wheat varieties
can be cultivated side by side for years without mixing."
Nilsson-Ehle (1915), in Sweden, has found that some varieties
show a much greater amount of natural crossing than others.
Howard and others (I910a), in India, carefully studied natural
crossing in wheat for several years and recorded 231 natural
1
FIG. 11. Natural wheat-rye
hybrids. Two spikes of parent
wheat varieties are shown on the
outside with hybrid spikes on the
inside. (After Leighty.)