. Bulletin. Agriculture. 20 TOBACCO BREEDING. crossing, for each flower is visited many times a day by various in- sects and often by humming birds; and, secondly, it brings about con- ditions favorable for the production of seed of weak vitality. Pre- vious experimenters have pointed out the fact that the best seed is not produced as a result of premature or late pollination, either of which is likely to occur in the case of tobacco flowers under natural con- ditions. When fertilized only by pollen of the same flower, the pollination takes place at exactly the right time, or when the stamens
. Bulletin. Agriculture. 20 TOBACCO BREEDING. crossing, for each flower is visited many times a day by various in- sects and often by humming birds; and, secondly, it brings about con- ditions favorable for the production of seed of weak vitality. Pre- vious experimenters have pointed out the fact that the best seed is not produced as a result of premature or late pollination, either of which is likely to occur in the case of tobacco flowers under natural con- ditions. When fertilized only by pollen of the same flower, the pollination takes place at exactly the right time, or when the stamens push past the receptive stigma, which results in the production of a superior grade of seed. The readiness with which tobacco flowers can be cross-fertilized greatly facilitates the opportunity for producing new and valuable varieties by artificial cross- ing. In the course of the experiments here recorded it has been found per- fectly possible to combine certain desirable qualities found in different strains and at the same time to eliminate some of the un- desirable characters by pro- ducing hj'brids between strains of tobacco. The method of cross-pol- lination used in the experi- ments of the writers is to remove all capsules, open flowers, and flower buds from the flower head ex- cept those which are in the proper stage of develop- ment to open within the following twelve or fifteen hours. In preparing these remaining flowers they must be carefully opened and emasculated by the use of a scalpel, small scissors, and a fine pair of forceps, as illustrated in figure 4. Great care must be taken in re- moving the anthers before they have dehisced, in order to avoid injury to the stigma. The emasculation should be done in the after- noon, after which all of the flowers must be carefully covered with a thin paper bag as a protection against insects or other agencies whereby pollen might be transferred to them. In the forenoon of the following day the emasculated flowers should be
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