"Section IV.—Transfers.
"Transfers of grain, together with all breeding privileges, may be made at any time, but in order that the progeny of such grain may be eligible to registry with the Association, each transfer must be entered for registry with the Recording Secretary of the Association within three months of the time of transfer. A certificate of transfer shall then be issued under the seal of the Association showing the record numbers under which the work of the breeders upon this corn has been recorded. A fee of $1 shall be charged for each record of transfer." How to cross plants.
One of the means of inducing variation, as already explained, is to cross one plant with another. By crossing, also, it may be possible to combine some of the attributes of two or more plants into one. The reader will want to know how crossing is accomplished.
For most farm purposes it is sufficient to grow the intended parents side by side, if they are wind or insect-pollinated, and let the chance of crossing rest with natural agencies. The seeds are then taken from the most likely parents and sown separately. In the progeny, one may expect to find some plants to his liking or at least such as are suggestive for further experiment. Plants that are freely visited by bees, as the fruit trees, or those in which the sexes are in separate flow ers, as maize and hemp and chestnuts and melons, are almost certain to be crossed by this method. If the stigma happens to receive pollen from its own flower or plant and also from another plant, the foreign pollen will usually accomplish the fecundation. No doubt a great many of our agricultural varieties have arisen from such natural and appar ently promiscuous crossing.
If one wishes to make an exact experiment, however, he must transfer the pollen himself under conditions of control, both to ensure that crossing takes place and that the pollen is from a given parent. The manual operation of crossing is of four parts : (1) protecting the pistil from undesired pollen ; (2) protecting the pol len; (3) applying the desired pollen; (4) protecting the ovary and fruit. The operator must first be familiar with the parts of the flower. If he has no teacher, he may secure this information from any of the school botanies : and Figs. 14 to 17 and 76 will aid him. In the succeeding pages he will find the flowers of the different crops displayed.
(1) Protecting the stigma.—If the flower contains stamens, the anthem must be removed before pollen is discharged. The discharge is likely to take place about as soon as the flower opens. The pistil must also be protected from foreign pollen. This means that the pistil must never be exposed to wind or insects. The protecting of the the pistil, then, is of two kinds,—removing the anthers (emascu lation), covering the flower. Usually the bud is opened just before it is ready to burst, the anthers clipped off or broken off, and the flower covered securely with a thin paper or muslin bag.
(2) Protecting the pollen.—In the meantime the pollen bearer has been looked after. It is safest to cover with a bag the flower or cluster of flowers from which pollen is to be taken, for insects may leave foreign pollen on the anthers. This precaution is not often taken, however, for the operator is careful to take his pollen only from unopened anthers. In some cases the pollen ripens in advance of the pistil, or it must be secured from a dis tance. It will usually retain vitality a few days if carefully dried (not heated) and kept dry in an envel ope. Some species have short-lived pollen, and some have relatively long-lived pollen : it should be the aim to have it as fresh as possible, when applied to the stigma.
(3) Applying the pollen.—Usually the stigma is not ripe or "receptive" when the flower is emasculated. The flower is to remain covered, therefore, until the: stigma is receptive. This epoch is determined by the looks of the stigma, a point to be accurately deter mined only by experience. The ripe stigma usually exudes a sticky or glistening covering, or it becomes rough and papillary. A hand lens will aid greatly in determining the proper time. A fresh ripe anther is crushed (if the pollen is taken fresh from the flower) on a knife-blade or thumb-nail, and some of the liberated pollen applied to the stigma by means of a needle-point or other small implement. The stigma is completely covered if possible. Then the bag is replaced.
(4) Protecting the forming fruit.—The bag is allowed to remain a few days, until all danger of further fecundation is removed. It is usually replaced by a mosquito-netting or tarlatan bag, in order to protect the fruit from insects or mechanical injury. This bag also aids in locating the fruit amongst