Hayes and Garber - Cucurbit Breeding

production. Methods of breeding
FLAX AND TOBACCO 159
essentially the same as with the small grains.
TOBACCO
for seed or fiber flax are
The Genus Nicotiana. The tobacco genus, Nicotiana, has
been divided by earlier workers into four sections: Tabacum,
Rustica, Petunioides, and Polidiclia (Don, 1838). More recently
the latter two sections have been combined (East, 1912a and
Setchell, 1912). East's conclusions were reached by crossing
N. Bigelovii, of the Petunioides section with N. quadrivalvis,
which was formerly placed in Polidiclia section. N. quadrivalvis
produces four-celled capsules and is a smaller plant than N.
Bigelovii. As the FI hybrid was entirely fertile, there seems no
good reason for placing these forms in different sections. The
four-celled capsule proved to be a partially dominant character.
From the standpoint of the student of plant genetics the
Nicotiana genus is especially favorable material. Some of the
reasons are:
1. Tobacco may be self-fertilized artificially with ease and the
technic of crossing is very simple.
2. Each plant produces a large number of seeds and the seed is
viable for many years.
3. There are a large number of varieties which are entirely
fertile inter se.
study of quantitative characters.
These furnish especially favorable material for a
4. The different species furnish very favorable material for a
study of sterility. Different crosses furnish FI generations which
differ from each other in sterility. The range extends from
species crosses which give no viable seed and from completely
sterile I