Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . pendent to a large extent upon the visits of insectsin the business of pollination. Insects are attractedto its service by the flaring advertisement of the showypetals; the nectar, which acts as a special lure; and alsoprobably by the pleasant scent of the flower. Pollengrains must be lodged on the stigma of the pistil, andit seems desirable that the pollen formed by one flowershould reach the stigma of a different flower. Thisinvolves cross-fertilization, which is thought to be abenefit
Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . pendent to a large extent upon the visits of insectsin the business of pollination. Insects are attractedto its service by the flaring advertisement of the showypetals; the nectar, which acts as a special lure; and alsoprobably by the pleasant scent of the flower. Pollengrains must be lodged on the stigma of the pistil, andit seems desirable that the pollen formed by one flowershould reach the stigma of a different flower. Thisinvolves cross-fertilization, which is thought to be abenefit to the species. A bee visiting a flower thrustsits proboscis down to the nectaries, and in doing so getsits head dusted with pollen; when it transfers its atten-tions to another flower it carries pollen to it, and someof it is sure to come in contact with the stigma. Thestigma, when ripe, secretes a somewhat sticky fluid, inwhich sugar is present. This fluid serves two purposes—it causes the pollen to adhere to the stigma, and alsoenables the grains to germinate. All Flowering plants Plate IX. J , GREATiiR SPEARWORT [Ranunculus!,Orsek Pelal 2. Fruit 3. i-ower leaf FEETILIZATION 175 do not invite insects to do the work of are other pollinating agencies, as we shall seelater. On germination, a pollen grain protrudes a pollentube, which forces its way between the cells of thestigma, penetrates into the tissue of the style, and ulti-mately reaches the ovary and one of the ovules containedtherein. The pollen tube enters the ovule through anopening known as the micropyle, and serves as apassage for the fertilizing male element, which, in theend, fuses with the egg-cell, or ovum, in the embryo-sac,such fusion being the real act of fertilization. Afterfertilization, the egg-cell develops into an embryo, andthe ovule containing the latter becomes a fertile pistil, which encloses the ovules, becomes the have said that the pollen g
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
