Miscellaneous- 



352 



[April 1908. 



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 varie- 

 ties of tobacco produced in the course of 

 these investigations. In most of these 

 districts certain men have become in- 

 terested in the careful and systematic 

 breeding of tobacco. 



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 crop 

 not only results in a low yield, as a 

 whole, and more especially of the best 

 and most profitable grades of the cure 

 and fermented product, but also in- 

 creases the cost of sorting out the differ- 

 ent types of leaves into their respective 

 grades for market, the expense of which 

 must be borne directly or indirectly by 

 the grower. 



The principal cause of the lack of the 

 uniformity in tobacco is cross-fertiliza- 

 tion. In tobacco, as in all other crops, 

 seed resulting from cross-fertilization 

 produces many plants unlike either 

 parent. Therefore such seed is undesir- 

 able for the general planting of a 

 crop where uniformity is so important 

 a factor. Where the tobacco seed 



Elants are grown without protection 

 roui cross-fertilization some of the 

 flowers are cross-fertilized by insects or 

 other agencies. Desirable plants may 

 thus be crossed with undesirable plants 

 in the same field or in the adjoining 

 fields, and the plants grown from the 

 seed thus produced are usually extremely 

 variable, some of them resembling the 

 desirable plants from which the seed 

 was harvested, others resembling the 

 inferior plants from which the pollen 

 was carried for crossing, while the re- 

 mainder are of an intermediate type, 

 unsuited to the purpose for which the 

 crop is grown, and therefore causing a 

 loss to the grower. The writers have 

 observed numberless cases in different 

 tobacco-growing sections where several 

 distinct and worthless new types ap- 

 peared in the fields, the plants of which 

 were g^own from carefully selected seed. 

 These undesirable types could only be 

 accounted for by the accidental crossing 

 of the seed plants the year preceding 

 or at some previous time. The crossing 

 of individual plants of the same strain, 

 even if both are desirable plants, results 

 in undesirable variations, many of which 

 are apparently reversions to earlier and 

 unimproved types of tobacco. 



In those varieties of tobacco in which 

 the buds are removed long before the 

 flowers open on all of the plants except 



those saved for seed production, or 

 where early topping is practised, the 

 opportunity for crossing of the flowers 

 borne by the seed plants with other 

 plants in the same field is almost wholly 

 limited to the seed plants. However, 

 it frequently occurs that late or diseased 

 plants, or possibly sucker branches that 

 have been overlooked, develop flowers 

 which open at just the right time to 

 allow insects to carry the pollen from 

 these flowers to the seed plants and thus 

 effect cross-fertilization. There is little 

 doubt that many of the plants of irre- 

 gular and unusual types are produced 

 as a result of this kiud of cross-fertili- 

 zation. 



An important cause of variation in 

 tobacco plants is the use of immature 

 seed. Many growers cut off or harvest 

 the seed heads before all the seed pods 

 have turned brown ; hence before 

 maturity. The writers have observed 

 hundreds of instances where the seed 

 plants have been cut off while many of 

 the flowers were still in bloom. On such 

 seed heads seed pods in all stages of 

 maturity can be found. Some of the 

 pods are fully ripe and contaiu mature 

 seed, while others have not fully deve- 

 loped. Much of the seed is immature 

 and coutains little food for the nourish- 

 ment of the plantlet. These seed heads 

 are frequently thrashed out with a flail 

 or the pods are crushed by haud in 

 order to shell out the seed. In this way 

 the immature seed is mixed with the ripe 

 seed sown in the seed beds. In the seed 

 beds the immature seed frequently 

 sprouts earlier than the mature seed, 

 and the early seedlings grown from such 

 seed are naturally seed for transplanting 

 in the field. Such plants have a great 

 tendency to vary, in some cases being 

 very early, and as a rule having leaves 

 that are small, coarse, and wholly un- 

 desirable for any purpose. These weak, 

 immature tobacco seeds, according to 

 careful and extensive observations by 

 the writers, produce plants which are 

 more subject to certain diseases, parti- 

 cularly the mosaic disease, than are 

 plants grown from mature seed. 



The excess of plant food in the soil 

 where heavy applications of barnyard 

 manure and commercial fertilizers are 

 used is usually thought to produce vari- 

 ations in the plants. This variation is 

 usually shown by an increase in the 

 size of the leaves, which is generally cor- 

 related with changes in colour, flavour, 

 and other characters. In these cases 

 there is usually a tendency for the type 

 of plant to break up, so that the unifor- 

 mity of the crop is disturbed. Where it 

 is necessary to use large quantities of 

 fertilizers in the growing of* a profitable 



