Fig. 96. Emasculated tomato-flower.
Fig. 97. Nicotiana affinis.
As soon as the flower is emasculated it must be securely tied up with a bag, to exclude pollen, as seen in [Fig. 100]. Netting of any kind is not safe in ordinary practice, for the pollen grains are small enough to pass through it. It often happens that the flower-stem is not strong enough to hold the bag, nor large enough to allow the bag to be puckered tightly about it. In such cases, all the remaining flowers in the cluster should be removed and the bag should be tied over a portion of the branch. The branch will often need to be cut off to accommodate the bag. If there are many large leaves about the flowers, part of them will need to be cut off. It is always a good practice to emasculate two or three flowers in the cluster—or all those of the same age—in order to multiply the chances of success. If flowers of different ages are emasculated, however, the bag will have to be removed several times to apply the pollen as the stigmas mature, and the chances of success will be lessened, for the flowers should be handled as little as possible.
Fig. 98. Crossed tomato.
Various bags have been devised and recommended for covering the flowers, but none of them yet introduced are equal to the ordinary grocers' manilla bags. The only difficulty is that the smallest size—the fourth-pound—is too large for many small subjects, but for these the bag can be cut off. A soft string, five or six inches long, is passed through one of the folds of the bag about an inch from the open end, as seen in [Fig. 101], and is tied to hold it in place. To make the bag pucker tightly about the stem, it should be moistened just before it is used.
In some flowers which have long and thick tube-like corollas, and in which the stigma matures quickly, the end of the corolla itself may be tied up. The flowers of squashes and pumpkins are particularly adapted to this treatment, and one is shown in [Fig. 102]. The flower is tied before it opens. In squash-like plants the flowers usually open early in the morning and the flowers are tied up the preceding evening. The corollas soon wilt and bags must be used after the pollen is applied; and even if the corolla does not wilt and shrivel, insects sometimes eat through it and interfere with the experiment.