54 TOBACCO BREEDING. 



In the breeding work conducted by the writers a portion of the 

 seed from the plants saved for seed is sown in small sections in the 

 seed beds and the plants are subsequently transplanted to separate 

 rows in the field. From the rows of plants producing the best type 

 and quality of tobacco further selections of seed plants are made. 

 In this way the productive capacity of the individual seed plants 

 can be tested and a record of their performance made by the breeder. 

 Usually 100 plants are grown from the seed of each seed plant in 

 the individual rows in the test plats. 



The sections of the seed beds necessan^ for producing this number 

 of plants at one time for transplanting are usually 3 by 3 feet in 

 size, boards one-half inch in thickness and 6 inches in width being 

 used for making the partitions. These boards are usually sunk in 

 the beds about 2 inches to prevent mixture of seed between the dif- 

 ferent sections. Necessariry the quantity of seed required to sow 

 these sections is very small, about 1 gram being used for this pur- 

 pose, which should be taken from the general seed product of the 

 individual plant. The seedlings from these sections can be trans- 

 planted by hand, care being taken not to injure the roots, and suffi- 

 cient water supplied to start the plants under favorable conditions. 

 This plan of testing the individual seed plants may not be practi- 

 cable for the grower of a small crop, but can be used to advantage 

 by tobacco breeders. 



After the seed plants have been selected in the field the flowers 

 should be protected from cross-fertilization and the seed saved in 

 accordance with the directions given under the head of methods of 

 saving seed. 



METHODS OF SAVING SEED. 



The absolute necessity of saving seed free from cross-fertilization 

 was recognized by the writers in the beginning of the tobacco-breeding 

 experiments. The readiness with which tobacco flowers are cross- 

 pollinated has been shown in a previous section, giving a description 

 of the flower, and has been emphasized all thru this bulletin. The 

 securing of pure, unmixt seed is necessarily of the first importance in 

 developing improved strains of tobacco which are sufficiently uniform 

 to meet the requirements of the manufacturers. After trying various 

 methods of keeping the seed pure by covering the flower head of the 

 plant it was found that the most practicable and efficient way to 

 protect the flowers from cross-pollination was by the use of a light, 

 strong manila paper bag, which serves to keep out all agents whereby 

 pollen may be transferred from plant to plant and from flower to 

 flower, and at the same time does not interfere with the proper 

 development of the flower head and the seed. This method impresses 



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