All imperfect flowers of course need no emasculation, but they must be tied up while yet in the bud to protect them from pollen.
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, and as it is carried upwards the pollen is secured.
Fig. 100. Flower tied up.
The stigma should receive an abundant supply of pollen. No harm can come from supplying too much while if too little is applied, some of the seeds will not mature or even the fruit may not set. It is well known that in many plants, at least, the pollen stimulates the development of the fruit-walls, as well as fertilizes the ovules, and a greater amount of pollen than is sufficient to produce the seeds themselves may therefore exert an important influence. Sometimes it is not necessary to use an instrument to transfer the pollen. If the pollen is copious and adheres to the anther after it is discharged, the anther may be simply rubbed over the stigma. An anther will ordinarily contain sufficient pollen to fertilize several stigmas. The whole surface of the stigma should be covered until it is colored with the pollen. Sometimes it will be found advisable to cut off the corolla from large flowers, if it was not done when the flower was emasculated, to facilitate the labor of applying pollen. The short stigmas of squashes, for instance, can be reached more easily if the corolla is removed, as in [Fig. 104].