GKEAT VARIABILITY OF TOBACCO PLANTS. 9 



ents, described in this bulletin, are good illustrations of the use of 

 breeding in the improvement of the tobacco crop. The making 

 and testing of hybrids are matters of experiment and require con- 

 siderable time and expense, but experience has shown that the 

 results justify the necessary expenditure. 



The production of improved breeds of live stock and varieties of 

 fruits and cereals, in fact, of all crops, might be cited to prove the 

 importance of apphdng the principles of breeding to the tobacco 

 crop. It is only recently that systematic breeding experiments have 

 been undertaken. It is hoped that the results of the experiments 

 cited in this bulletin will serve as a means of creating general inter- 

 est in this subject and of inducing investigators, breeders, and grow- 

 ers to turn their attention to the further improvement of their crops. 



Tobacco growers in the sections where these experiments have 

 been carried on have generally adopted the improved methods of 

 bagging carefully selected seed plants and of separating the seed, 

 and they are using the improved varieties of tobacco produced in 

 the course of these investigations. In most of these districts cer- 

 tain men have become interested in the careful and systematic breed- 

 ing of tobacco. 



THE GREAT VARIABILITY OE TOBACCO PLANTS. 



Under the intensive system of cultivation necessary for the pro- 

 duction of profitable crops of tobacco, the condition of the soil, 

 the fertilization, and the cultivation are fairly uniform so far as 

 individual fields are concerned. In those tobacco-growing sections 

 where the best grades are produced it is a common practise to grow 

 tobacco year after year on the same field without rotation, instances 

 being known where more than fifty consecutive crops have been pro- 

 duced on the same field. This system of cropping enables the grow- 

 ers to become thoroly familiar with the character of the soil in all 

 sections of the fields, so that any inequality in fertility can be reme- 

 died by the judicious application of manures or commercial fertili- 

 zers, or by methods of cultivation. Notwithstanding these favorable 

 circumstances for the production of uniform plants, a careful study 

 of the plants in these fields reveals a great lack of uniformity as 

 regards all characters. This lack of uniformity is particularly 

 noticeable with respect to the variation in number, size, venation, 

 shape, and habit of growth of the leaves borne by individual plants, 

 the time of ripening of the leaves on the same plant and on diiferent 

 plants, the number and size of the suckers, and the structure and 

 arrangement of the flowers and flower heads. From the practical 

 standpoint, there is no more important problem in tobacco culture 

 than the production of uniform crops. A lack of uniformity in the 



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