Trees and shrubs, hardy in the British isles . )and the pistil (female). The process of fertilisation or impregnation isbrought about by the transference of pollen (usually a minute yellowpowder borne in sacs called anthers at the top of the stamen) to thesummit of the pistil. The pistil has three parts; at the base is the ovary,a swollen body which contains the incipient seeds, or ovules; above thatis a stalk of varying length called the style, bearing at the top a knob(ultimately viscid), called the stigma. It is upon the stigma that thepollen must lodge so that the ovules may be changed int
Trees and shrubs, hardy in the British isles . )and the pistil (female). The process of fertilisation or impregnation isbrought about by the transference of pollen (usually a minute yellowpowder borne in sacs called anthers at the top of the stamen) to thesummit of the pistil. The pistil has three parts; at the base is the ovary,a swollen body which contains the incipient seeds, or ovules; above thatis a stalk of varying length called the style, bearing at the top a knob(ultimately viscid), called the stigma. It is upon the stigma that thepollen must lodge so that the ovules may be changed into fertile seeds. Whilst Nature adopts various methods to prevent the fertilisation ofa flower by its own pollen (often by the non-synchronous ripening of thepollen and receptivity of the stigma ; often by separating the sexes ondifferent plants), her intention is that the impregnation should be doneby pollen from a flower of the .same species. Thus whilst, in the highergroups, she abhors in-breeding, she also objects to mules. The hybridiser,. <J) HYBRIDISING AND SELECTION 27 on the other hand, has to bring about the fertihsation of the flower of onespecies or variety by the pollen of another of his own choosing. His aimis usually to unite in the progeny qualities in the parents severallypossessed, such as hardiness or better habit with greater flower are limits, of course, to the choice of parents, just as there are inthe animal world. Species of the same genus are capable as a rule ofbeing hybridised, although sometimes physical divergences prevent , too, species of different but closely allied genera will cross-breed. Progeny of the more distantly related parents are generallybarren. To secure hybridisation two essential points must be borne in mind:viz., the stigma should be in a receptive condition, and the impregnationof the flower by pollen from any other flower than the one selected by theoperator must be prevented. The stigma usually indi
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