FLAX AND TOBACCO 159 



production. Methods of breeding for seed or fiber flax are 

 essentially the same as with the small grains. 



TOBACCO 



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. These furnish especially favorable material for a 

 study of quantitative characters. 



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 FI crosses, to entirely fertile ones. 



The Tabacum section is represented by numerous varieties 

 of the species Nicotiana tabacum. These are natives of the 

 New World. All commercial tobacco grown in the United 

 States belongs to this species. 



The Rustica section includes all the yellow-flowering species 

 and varieties. These are of commercial importance in some 

 countries. In India for example, they are successfully grown 

 commercially and for some purposes prove more desirable than 

 the tabacum varieties (Howard, et al, 1910 b,c). Among these 

 rustica forms are three groups; (a) one in which the pistil is 



