150 PRINCIPLES AND CONCLUSIONS. 



Anemophilous flowers. — In his study of the attraction of anemophi- 

 lous flowers (1897:601), Plateau enumerated Chenopodium album, Rumex 

 obtusifolius, Corylus avellana, Carex, Anthoxanthum, Agrostis, Poa, Festuca, 

 Bromus, Brachypodium, and Secale as already known to be visited by insects 

 for their pollen, and cited also a number of cases in which extrafloral nec- 

 taries and fruits were visited by bees and butterflies. His own experiments 

 were carried out on green or brownish flowers belonging to the Chenopo- 

 diaceae, Urticaceae, Polygonaceae, Typhaceae, Juncaceae, Cyperaceae, 

 and Poaceae, to which honey was added. The great majority of the visitors 

 were Diptera, which usually came within a few minutes, while the bees 

 appeared much later. It is perhaps significant that Apis went to 12 of the 

 17 species, the wasps Odynerus and Vespa to but 4, and Bombus to but 1. 

 Rheum tataricum, which combines the two methods of pollination to some 

 degree, gave somewhat similar results with honey, but Apis was entirely 

 absent and 2 species of Bombus made one visit each. 



Entomophilous flowers of dull color. — After citing the frequent 

 neglect of such flowers by Darwin and Mueller, and the emphasis upon 

 their significance by Bonnier and MacLeod, Plateau (1897:613) gave a 

 complete summary of his own and other observations upon flowers of this 

 type, grouped as green, greenish, brown, or brownish. In the first group 

 he listed 43 species belonging to 18 families, frequented chiefly by Diptera, 

 especially the muscids; 8 species were visited by Apis, 4 by Bombus, and 8 

 by other bees, usually the same ones. In the group with greenish flowers or 

 inflorescences were placed 38 species belonging to 20 families, of which 10 

 were visited by A pis, 4 by Bombus, and 6 by other bees, the vast majority 

 of visitors being flies. The flowers with brown or brownish color numbered 

 12 and were distributed in 9 families, 6 of the species being visited by honey- 

 bees. 



In the matter of anemophilous flowers the conclusion was reached that 

 it was only necessary to add honey in order to attract insects in large 

 numbers. Moreover, insect visits were abundant to 91 species of ento- 

 mophilous plants that lack striking color in the corolla. In short, insects 

 concern themselves little with the presence or the absence of bright floral 

 parts; what they desire is pollen or nectar. They are guided to these in 

 a very secondary degree by sight, but on the contrary in a sure manner 

 by another sense, which can only be that of smell. 



Artificial flowers, second series. — The first experiments of Plateau, 

 made by means of artificial flowers in 1876, were augmented 20 years later 

 by studies with the flowers of 8 different families (1897:847). In all cases 

 the flowers were copied with the utmost fidelity, even to the details of 

 stamens, calyx, etc. With Ribes sanguineum 10 clusters of artificial flowers 

 were placed among normal ones, but of 5 individuals of Bombus, 3 of Apis, 

 and 3 of Osmia, not one was seen to pay the slightest attention to them. 

 Two branches of artificial flowers of the peach were suspended among the 

 natural ones and observed for three different periods two days apart. The 

 bees showed complete disdain for the imitation flowers, even when they 

 were supplied with a drop of honey, as on the last day. With flowers of the 

 cherry the results were the same, bumble-bees and honey-bees both passing 



