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SCIENCE-GOSSIP. 



ever, the question was put with snapdragon the 

 answer seemed different ; insects did not visit the 

 remaining green parts. Professor Plateau thinks 

 this may have been because the mouth of the green 

 calyx of this flower is directed upwards, while 

 insects generally attack such flowers from below. 

 In any case one negative answer cannot alter the 

 obvious conclusions from the many positive ones. 



Another answer to the question comes from the 

 well-known fact that insects pass freely from one 

 colour to another among our garden flowers. 

 Professor Plateau rightly claims this as supporting 

 his view. He himself has seen them pass freely 

 from colour to colour in a bed containing blue, 

 purple, rose, and white cornflowers ; in a patch 

 of red, scarlet, purple, rose, yellow, orange and 

 white single dahlias ; and from the vivid red of 

 the garden flax to the bright blue of the common 

 flax. Other writers, including Darwin, have 

 observed the same thing. 



The question, however, may be put in another 

 form. There are certain brilliantly-coloured 

 flowers which insects scarcely ever visit. Now, if 

 insects are attracted rather by perceiving in some 

 way that honey is present than by the colours of 

 flowers, then they ought to be attracted to such 

 flowers when honey is placed in them. So 

 Professor Plateau chose the scarlet geranium of our 

 gardens, and placed seme honey on a few of the 

 flowers. In the course of an hour these honeyed 

 flowers were visited by eight humble bees ; and 

 when these bees, in the course of gathering honey 

 from these honeyed flowers, came to those without 

 it, they flew over them without alighting. Phlox, 

 Japanese anemone, and the larger bindweed were 

 treated in the same way, and with similar results. 



Again, if the honey-bearing parts of flowers be 

 removed, leaving the gay corolla, then, if insects 

 are not attracted chiefly by colour, they should 

 cease to visit them. The question was then 

 put in this form. The central florets of single 

 dahlias, which alone secrete honey, were carefully 

 removed, and bits of yellow leaf put in their place. 

 No insects came to visit the flowers thus treated. 

 As soon as a drop of honey was placed on these 

 artificial discs, then insects were attracted as freely 

 as before. The discs were then removed, and a 

 little honey placed in the central space. Again 

 insects were quickly attracted. 



Another answer comes from the habits of insects 

 in visiting flowers. There are a number of plants 

 with inconspicuous flowers, usually fertilized by the 

 wind, and hence known as " anemophilous." These 

 have no gaily-coloured corollas to advertise their 

 honey or pollen, yet not a few of them, as certain 

 species of Chenopodimn, nut, docks, rushes and grasses 

 are, on authority of various authors, visited by 

 insects. Insects would not visit these flowers if they 

 required the stimulus of colour to attract them. 



Yet again, the question may be put in another 

 form. If insects are attracted to flowers not by 

 gay colour, but by the perception of honey, then 

 if honey be placed in such inconspicuous anemo- 

 philous flowers as are seldom or never visited by 

 insects, the latter ought then to be attracted. 

 This was found to be the case. Honey was placed 

 on seventeen species of such flowers, including 

 Chenopodium, hemp, hop, nettles, reeds and grasses, 

 and in each case insects were attracted. 



We ought also to obtain an answer to our 

 question by noting the colours of flowers freely 

 visited by insects. If they are chiefly drawn by 

 gay colours, then we should expect to find them 

 rather avoiding the green and inconspicuous ones. 

 So Professor Plateau brings forward a list of 

 green, greenish, brown, or brownish flowers, freely 

 visited by insects. This list, containing ninety-one 

 species in all, includes such flowers as helle- 

 bore, ladies' mantle, ivy, currants, figwort, spurge, 

 asparagus, lime, sycamore, raspberry, wood sage, 

 etc. All these, on the authority of Professor 

 Plateau himself and others, are freely visited. 



Professor Plateau's final questionings were made 

 with artificial flowers. These were made to imitate 

 lilac, forget-me-not, saxifrage and foxglove. Being 

 placed among natural flowers they entirely failed 

 to attract insects. Even when honey was placed 

 in them none came. Obviously, then, insects are 

 not attracted by such artificial colours. The fact 

 that even honey failed to bring them seems to show 

 that they had some distrust of the artificial flowers. 

 Then Professor Plateau altered the form of this 

 final question. He now made some artificial 

 flowers of bits of green leaves of red currant and 

 of sycamore, placing a little honey in each. To 

 these strange looking flowers, unlike anything they 

 had seen before, insects came freely for the honey. 



From all this cross-questioning of nature Pro- 

 fessor Plateau claims to be entitled to draw the 

 following conclusion : " Insects seem to care little 

 either for the presence or absence of floral parts of 

 brilliant colours. That which they desire is pollen 

 or nectar, and they are guided in a very subordinate 

 way by sight, but on the contrary in a sure way by 

 another sense, which can only be smell." 



If we admit his facts we cannot escape from 

 Professor Plateau's conclusions; no explaining 

 away is possible. But if we accept the inference 

 that insects are not attracted to flowers by their 

 gay colours, can we retain a belief in the insect 

 selection theory of the origin of flowers ? Giving 

 up the assumption that brilliant colours are the 

 attraction and guide to insects, we take away a 

 plank from the hull of the little barque of theory 

 which has sailed so gaily these many summers 

 over the seas of popular scientific literature ; and 

 the leak is fatal. 



29, Queen's Terrace, Jesmond, Newcastle-on-Tyne. 



