. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 2o8 SUPPLEMENT TO THE INTRODUCTION cation), I was at first more than surprised to hear of these experiments, for they seemed entirely to overthrow a view which I had up to that time considered an established oecological fact. But on careful consideration of these experiments, I came to the conclusion that Plateau's inferences are not justified, and that another explanation is permissible. Let us take the experiment made with Digitalis purpurea. Plateau cut a

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. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 2o8 SUPPLEMENT TO THE INTRODUCTION cation), I was at first more than surprised to hear of these experiments, for they seemed entirely to overthrow a view which I had up to that time considered an established oecological fact. But on careful consideration of these experiments, I came to the conclusion that Plateau's inferences are not justified, and that another explanation is permissible. Let us take the experiment made with Digitalis purpurea. Plateau cut away not only the corolla-tube but also the style and stamens, till only a stump I cm. long remained (see Fig. 80). Gaston Bonnier ('Les Nectaires,' 1879, p. 61) observed many years ago that 'les abeilles continuent k visiter en meme nombre les Digitales sur les pieds oil toutes les couronnes avaient ete enlevees.' Plateau's experiments confirmed this observation, for the visitors of uninjured flowers (Bombus terrester L. and Anthidium manicatum Z.) also sucked the mutilated ones, finding it hard work to hold on while doing so—the resting-place presented by the complete corolla being absent. 'Ainsi,' says Plateau, 'les hymenopteres visitent encore, et d'une fafon effective, les fieurs de Digitales n'ayant plus ni leur couleur attractive, ni des dimensions les rendant trfes visibles, ni la forme que ces animaux ont coutume d'utiliser pour parvenir aisement au nectar.' But if we remember that a mutilated flower is an open cup, containing nectar which is constantly renewed from the base of the flower—-where the nectar is situated—we shall realize that this nectar is freely displayed after removal of the corolla, and therefore—being exposed to the direct action of sunshine and wind— must evaporate more quickly, give out a stronger odour, and attract more strongly than when it is hidden at the bottom of a long corolla-tube. The visits of insects to this exposed nectar-cup w

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