4 CIRCULAR 249, U. S. DEPARTMENT OF AGRICULTURE 
differentiated and for which there is an established demand are as 
follows: 
(1) The character of the soil in which the tobacco is grown 
No crop is more susceptible to slight changes in soil and subsoil than tobacco. 
Soil is the chief determining and limiting factor. There are a few localities where 
two or more types can be grown interchangeably, such as the Miami Valley dis- 
trict of Ohio, and the Connecticut Valley, in each of which three different types 
of cigar tobacco are grown. Even here it should be noted that the interchangeable 
types are rather closely related in the sense that all are especially adapted to the 
manufacture of cigars. In addition there are, as has been previously indicated, 
very limited transition zones wherein types are alternated or shifted. 
(2) The climate in which the tobacco is grown 
Climatic factors include the temperature range, normal precipitation, relative 
humidity, and relative number of hours of daylight. 
(3) Variety of seed 
The different varieties of tobacco have been bred under certain soil conditions 
to meet specific requirements. These varieties, if transferred to a new environ- 
ment, would immediately lose some of their characteristics and consequent value. 
(4) Methods of cultivation, fertilization, and harvesting 
These relate particularly to the qualities obtained by the choice of cultural 
methods. Under cultivation are included such questions as spacing between 
plants, and time and height of topping, which affect the thickness of the leaf, 
and growing under shade or open field. Fertilization and methods of harvesting 
(priming or stalk cutting) have important effects, especially on the burning. 
qualities and color. 
(5) Method of curing 
Types of tobacco are grouped largely according to the three curing methods 
practiced. The effects of curing upon the color, finish, and aroma of the tobacco 
vary. The effects obtained by the flue-curing method upon the varieties grown 
under the soil and climatic conditions prevailing in the recognized flue-cured 
districts would not be obtained if applied in Maryland or other air-cured districts, 
or in the fire-cured districts. Conversely, tobacco in the flue-cured district, if 
cured by air-curing or fire-curing technique, would fail to achieve the qualities 
and characteristics of the recognized air-cured and fire-cured types. Again, if 
seed from the heavy-bodied types of western Kentucky, Tennessee, or elsewhere 
were introduced into the Atlantic Coastal Plain it would not, even with flue-curing 
methods, develop the true characteristics of flue-cured tobacco. 
The association between soil, seed, climate, and cultural and curing practices 
is so close and has such a determining effect upon the type produced as to pre- 
clude, as a general rule, the duplication of any given type in a new environment. 
The cases where growers can successfully shift from one type to another are so 
few that they serve to emphasize the general rule to the contrary. 
CLASSES AND TY PES OF AMERICAN-GROWN TOBACCO 
Classes of tobacco differ from each other in important respects. 
Types within a class differ in minor respects. The contrasts between 
classes, such as flue-cured, fire-cured, etc., result not only from the 
differences in curing methods, but from variations in soils, cultural 
practices and climate. The contrasts between the large, heavy, 
gummy, dark-brown leaves of fire-cured tobacco and the thinner, 
brighter colored leaves of flue-cured tobacco, or the papery leaves of 
Burley and Maryland, for example, are very marked. 
The flue-cured tobacco, instead of being heavy and gummy, is of 
light body, fine texture and oily, but relatively free from gum. To 
