CONSPICUOUS FLOWERS RARELY VISITED BY INSECTS 151 



equally applicable to color. Neither color nor odor separately 

 or together will attract insects continuously, if they can obtain 

 no spoil. 



Plateau was equally mistaken in supposing that the addition 

 of an agreeable odor is indispensable; for it is only necessary to 

 introduce a solution of sugar and water, which is odorless, to 

 bring insects to the flowers in great numbers, as will be shown 

 experimentally. In the absence of accessible food materials 

 pleasantly scented flowers will not be visited more frequently 

 than would be the case if they possessed only bright coloration. 

 Insects will not repeatedly visit an inflorescence because they 

 experience an aesthetic pleasure. This is well shown by Lathyrus 

 odoratus L., or the sweet pea, which, notwithstanding its strong 

 fragrance and brilliant hues, is very rarely sought by insects, 

 because the nectar is inaccessible to nearly all of them. An 

 ample, available food supply will alone secure continued and 

 frequent visits of insects to flowers. Since it can be shown, 

 therefore, that an inflorescence can be rendered very attractive 

 to insects without the addition of an odor, it logically follows 

 from Plateau's own method of reasoning that conspicuousness 

 is beneficial. 



When Plateau introduced honey into certain selected flowers, 

 they received two allurements, an agreeable odor and a sweet 

 liquid food, which sharply distinguished them from the flowers 

 left in their natural state. In effect, the flowers containing 

 honey became distinct physiological varieties. Color and odor 

 were not brought, therefore, into competition on equal terms; 

 the flowers in their natural state possessed only color and 

 form, while those into which honey was introduced possessed 

 color, form, an agreeable odor and a liquid food. Manifestly, 

 the latter flowers were given the greater advantage, and it is 

 unfair to conclude that because they received the greater num- 

 ber of visits, odor was essential and color was of no significance. 

 Throughout Plateau's experiments, the presence of the vexillary 

 organs was a source of error. As he had assumed that they 

 were of no value, it is difficult to understand why he did not 

 remove the floral envelopes, when the flowers would of necessity 

 have been compelled to depend wholly on the odoriferous liquid 

 food. Finally, to have made the competition impartial, an odor- 



