22 TOBACCO BREEDING. 



THE NECESSITY FOR INBREEDING. 



In the season of 1903 the writers, in company with Dr. H. J. "Web- 

 ber, visited the tobacco fiekls of the Connecticut Valley in response to 

 a request of the growers for assistance in the production of uniform 

 strains of tobacco by breeding and seed selection. During the survey 

 of this region with a view to gaining an idea of the variability of the 

 varieties of tobacco, it was determined to inaugurate a series of ex- 

 periments in a practical way for the investigation of the methods of 

 saving seed. 



In view of the results of the investigations of Darwin and others 

 on the comparative vigor of growth, seed production, and other char- 

 acters of tobacco plants raised from seed obtained by cross and by self 

 fertilization " the seed of select plants of the different tvpes of tobacco 

 was protected from cross-fertilization by inclosing the flower heads 

 with a light but strong form of paper bag. Other seed plants were 

 saved without such protection, as is ordinarily done by the tobacco 

 growers. The seed harvested from these seed plants was saved sepa- 

 rately, stored in small glass vials adapted to this purpose, and labeled 

 according to the system now in use by the breeders in the plant breed- 

 ing investigations of the United States Department of Agriculture. 

 The record of the number of leaves, size, thickness, shape, and color of 

 leaves, number of suckers, height of plant, habit of growth of leaves 

 and plants, time of maturity of leaves and seed, and other characters 

 was kept according to the system used by Doctor Webber, modified 

 by the writers for use in keeping a pedigree of tobacco varieties. 



The seed of the plants finally selected for experimental purposes 

 was sown in ordinary seed beds, separated into many small sections 

 by thin board partitions, each of which was capable of holding 500 

 seedlings. The seedlings from these separate seed-bed plats were 

 transplanted to separate rows or plats in the experimental field, each 

 row or plat being carefully labeled so that the plants could be traced 

 directly back to the original seed plants. The manuring, or fertili- 

 zation, and preparation of the soil in the experimental field and the 

 transplanting, cultivation, and harvesting of the plants were all 

 conducted with the greatest possible care to give all of the rows or 

 plats equal opportunity for growth. For instance, the seed of all of 

 the plants of a variety was sown the same day, and at the proper 

 time the seedlings of this variety were all transplanted the same day. 

 At the time of harvest the leaves of the individual rows or plats were 

 primed or the plants cut on the same day, and the leaves or plants 

 were hung in the curing shed, so as to get as nearly uniform condi- 



1 Darwin, Charles. Cross and Self Fertilization in the Vegetable Kingdom, 

 pp. 203-215. 

 96 



