Hayes and Garber - Cucurbit Breeding

INTRODUCTION 5
(1750) had a pistillate palm in Berlin which was 80 years old
and had set no seed. He obtained a quantity of pollen from
trees in Leipsic (then nine days' journey from Berlin) and after
pollination seed was produced which germinated.
The Studies of Koelreuter. 1 While these investigators and
others confirmed the work of Camerarius, little advance was made
in the art of breeding until Koelreuter (1761) made a careful
study of artificial crosses and gave the first extended account.
In tobacco crosses, for example, he found that the first generation
was of intermediate habit and therefore showed the effect of the
male parent. His work on the vigor of first generation crosses
is of much interest. He believed the "oil" of the pollen grain
'after mixing with the stigmatic fluid penetrated the ovule. The
belief of a union of male and female substances was a step in
the right direction. The value of insects as carriers of pollen
was also demonstrated.
Early Studies in the Cytology of Fertilization. Pollen tubes
were first observed in 1823 by Amici who followed them to the
micropyle of the ovule in 1830. Schleiden shortly afterward
made numerous studies of the pollen tube and apparently thought
the embryo developed in the embryo sac from the end of the
pollen tube. This matter was not thoroughly cleared up until
Strasburger (see Johnson, 1915) concluded, in 1884, that:
"1. The fertilization process depends upon the copulation with the
egg nucleus of the male nucleus which is brought into the egg. 2. The
cytoplasm is not concerned in the process. 3. The sperm nucleus, like
the egg nucleus, is a true cell nucleus."
An Answer to the Question of Hybrid Fertilization. Although
Koelreuter proved the fact of sexuality in plants it
was not generally accepted, and early in the nineteenth century
the Physical Section of
the Royal Prussian Academy offered a
prize for an answer to the question, "Does hybrid fertilization
occur in the plant kingdom?" Among other results presented
by Weigmann in answer to this question occurs the statement of
the immediate effect of pollen in legumes. Weigmann made a
study of 36 crosses using the following plants: onion, cabbage,
pea, bean, lentil, pink, and tobacco. He observed the fact of
variability due to crossing and thought gardeners should pay
1
For these facts the papers of other writers have been freely used. Those
by ROBERTS (1919) have been especially helpful.