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. All imperfect flowers of course need no emasculation, but they must be tied up while yet in the bud to protect them from pollen. [Illustration: Fig. 99. Crossed and uncrossed gooseberries.] As soon as the stigma matures--which will vary from one to six or seven days, according to the species--the pollen must be applied. The novice will be obliged to remove the bags occasionally, to see if the stigmas are ready. As soon as the shiny or glutinous appearance of the stigma is seen, pollination should be performed. The pollen is most easily secured by removing an anther when it is about to burst and breaking it open. If the anther is allowed to break open naturally, the pollen will be lost, or at least difficult to secure. There are various instruments recommended to aid in the transfer of the pollen. A camel's hair brush is often advised, but it is probably the poorest instrument which can be used. It wastes the pollen and also mixes it by holding it among the hairs, and it is often a difficult matter to apply pollen to the stigma evenly and in sufficient amount. The point of a small knife-blade is a better instrument. A still handier and better tool is made by flattening the point of a pin and then inserting the little scalpel in a handle, as shown in Fig. 103. With the point of this implement the pollen can be removed from the groove or opening in the side of the anther. It is commonly better, however, to place the unopened anther upon the thumb nail and crush it with the scalpel, when the pollen can be gathered up on the point and transferred to the stigma. In some species the pollen can be removed only by opening the anther-valves dexterously. Such is the case with the tomato; the point of the scalpel is inserted in a longitudinal groove or fold in the side of the anther,