The evolution theory . g power of the pollen-cell in self-fertilization stand in inverse ratio to the length of the pistil, as has 254 THE EVOLUTION THEORY been proved in regard to heterostylism by Strasburger; but in anycase it was possible for Nature, by means of slight variations in thecharacters of the male and female parts of the fioAver, to diminish thecertainty of the meeting of the two germ-cells, even to the total exclu-sion of the possibility of any union of these. If, then, self-fertilization had to be guarded against or at leastrendered difficult because its consequences were injur
The evolution theory . g power of the pollen-cell in self-fertilization stand in inverse ratio to the length of the pistil, as has 254 THE EVOLUTION THEORY been proved in regard to heterostylism by Strasburger; but in anycase it was possible for Nature, by means of slight variations in thecharacters of the male and female parts of the fioAver, to diminish thecertainty of the meeting of the two germ-cells, even to the total exclu-sion of the possibility of any union of these. If, then, self-fertilization had to be guarded against or at leastrendered difficult because its consequences were injurious, all variationspointing in the direction of safeguarding would necessarily be pre-served and increased. In many cases variations in the structureof the flower were sufficient; but when, as in Corydalis cava, the pollencould not readily be prevented from falling upon the stigma, thepollen might be made sterile as far as its own flower was concernedby a process of selection, in which on an average those plants would.
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Keywords: ., bookauthorthomsonj, bookcentury1900, bookdecade1900, bookyear1904
