STRUCTURE AND AHHANGEMENT OF FLOWERS. 21 



parent plant can be best applied to the stigma of the female with the 

 point of a scal])el or other sharp instrument. When applied with a 

 brush there is danger of some of the pollen grains adhering to the 

 hairs of the brush after each o[)eration, resulting in considerable 

 mixture of pollen, but where the scalpel is used there is no difliculty 

 in removing all the pollen after each operation. The paper bag 

 must be replaced over the flowers as soon as they have been pol- 

 linated, and must be allowed to remain until the seeds have set and 

 all danger of crossing has past. 



In crossing it is not essential that both of the parent varieties be 

 grown in the same conmiunity. Pollen from tobacco flowers when 

 thoroly dry will keep for several weeks or longer without deteriora- 

 tion. The writers have sent pollen thru the mails a distance of more 

 than a thousand miles with perfectly satisfactory results. When 

 not intended for innnediate use, it should be harvested when perfectly 

 dry and carefully taken otf the anthers after they have dehisced 

 and become dried out. These dry anthers may be put in small 

 vials, and the pollen kept long enough for all practical purposes, 

 provided the vials are carefidly corked and kept dry. 



The large number of seed produced in a single pod and on a single 

 plant makes it possible to obtain definite results from selection or 

 hybridization in tobacco much more quickly than in the case of most 

 other i)lants. Careful counts show that from 4.000 to 8.000 seeds are 

 produced in a single pod of nornuil size, and an estimate of the aver- 

 age number of pods on each plant shows that the ordinary tobacco 

 plant produces from 500,000 to 1,000,000 seeds. In many cases the 

 writers have secured from 1 to 1| ounces of seed from a single plant 

 when the seed has been saved under bag according to the method out- 

 lined in this bulletin. This large number of seeds gives an excellent 

 opportunity for testing each selection or cross on a large scale. The 

 quantity of seed produced varies inversely with the number and size 

 of leaves on the plant. The production of a large number of good- 

 sized leaves is almost invariably accompanied by the production of a 

 small quantity of seed. 



On account of the large quantity of seed produced l^y a single 

 plant under normal conditions and the fact that the various charac- 

 ters of a tobacco plant are inherited so strikingly and uniformly by 

 its progeny the following year when the seed is saved under bag, pro- 

 tected from cross-fertilization, it is possible for the tobacco grower 

 to secure uniformity with a considerable degree of improvement in 

 type, quality, and yield by one year's selection. One plant often fur- 

 nishes enough seed for an entire crop, and the plants raised from this 

 seed always produce a very uniform lot of tobacco when cross-fertili- 

 zation is not allowed to take place. 



96 



