CONSPICUOUS FLOWERS RARELY VISITED BY INSECTS 149 



by the characters of various natural flowers. The cornflower, 

 {Centaur ea Cyanus L.), Gentiana acaulis L., and several other 

 gentians have conspicuous nectariferous flowers, which are visited 

 by numerous insects although they are devoid of scent. Bees 

 frequently gather pollen from poppy flowers, which are not only 

 nectarless but possess a faint unpleasant odor. From the wind- 

 pollinated, purple flowers of the elm, which are both nectarless 

 and odorless, honey-bees in immense numbers sometimes procure 

 pollen for early brood-rearing; while many other anemophilous 

 species are also valuable to the bee-keeper as sources of pollen. 

 Nor is it stated that there are many conspicuous flowers, which 

 are neglected by insects notwithstanding they are strongly 

 odoriferous, as the sweet pea, Lilium candidum, and varieties 

 of Pelargonium, which have the entire plant pleasantly scented. 

 Finally, if a flower is rich in nectar, it may be both inconspicuous 

 and odorless and yet receive numerous visits. According to 

 Fritz Muller, there is in South Brazil a species of Trianosperma 

 which is visited very abundantly all day long by Apis mellifera 

 and species of Melipona, although the flowers are scentless, 

 greenish and to a great extent hidden by the foliage.' It is 

 thus apparent that the visits of insects in large numbers are not 

 dependent on the presence of an agreeable odor. 



But, assuming the validity of his conclusion that bright 

 coloration is without significance because certain conspicuous 

 flowers are commonly neglected by insects, Plateau performed 

 a long series of experiments, in some instances introducing honey 

 and in others odoriferous sweet syrups into neglected flowers 

 with the result that in most cases insects were attracted, often 

 in large numbers. In his earlier experiments of 1897, he em- 

 ployed only honey diluted with water. When a small quantity 

 of this mixture was placed on the handsome flowers of Pelar- 

 gonium zonale, Phlox paniculata and Anemone japonica, it was 

 speedily discovered by numerous Diptera and Hymenoptera. 

 Similar results were obtained with greenish or dull-colored flowers. 

 The vexillary organs are, therefore, asserted to be of little or 

 no importance. « 



Knuth considered these experiments of no value since " they 



i Muller, H., " Fertilization of Flowers," p. 270. 



» Plateau, F., "Comment les fleurs attirent les insectes," 3me part., Bull, de V Acad, 

 roy. de Belgique, 33:27-37, 1897; 4me part., loc. cit., 34:604-10, 1897. 



