. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. HOW FLOWERS ATTRACT INSECTS 209 that were uninjured, it follows that the brightly coloured corolla exerts an attrac- tive influence. It was only in the case of Antirrhinum majus that the mutilated flowers received no visitors. After Plateau had cut down a number of such flowers till they were only I cm. long, the humble-bees (Bombus terrester Z.) which were sucking the uninjured blossoms showed no inclination to visit them. Plateau tries to explain this by s
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. HOW FLOWERS ATTRACT INSECTS 209 that were uninjured, it follows that the brightly coloured corolla exerts an attrac- tive influence. It was only in the case of Antirrhinum majus that the mutilated flowers received no visitors. After Plateau had cut down a number of such flowers till they were only I cm. long, the humble-bees (Bombus terrester Z.) which were sucking the uninjured blossoms showed no inclination to visit them. Plateau tries to explain this by saying that in order to reach the nectar of the mutilated flowers—which are open above—by flying up from below, the insects could get no foothold except by suddenly converting their ascending movements into descending ones. For this reason they preferred to forgo the use of the nectar in the mutilated flowers, and to seek out uninjured blossoms in the neighbourhood. This explanation does not seem to me to be a happy one, because these insects settle on many other flowers from above, without suffering any inconvenience from this mode of alighting. It appears to me far more probable that ike odour 0/ Anti- rrhinum majus is not sufficient /or purposes of attraction, but that here the form and colour of the corolla play a leading part in this matter, so that the insects do not visit mutilated flowers in which these means of allurement are wanting. Plateau conducted a most interesting experiment with Centaurea Cyanus. He removed the blue ray-florets—which according to our view merely serve to attract and are therefore neuter—leaving only the rather inconspicuous disk-florets {see Fig. 81). In spite of this many bees (Megachile ericetorum) visited the cornflowers so treated. Plateau sup- poses that the insects were attracted by the odour. I believe that this occurrence is quite as easily explained by assuming that the visitors of intact cornflower capitula have become ac- quai
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