210 SUPPLEMENT TO THE INTRODUCTION 
near, but would be able to perceive it at a greater distance, and would then 
turn aside. 
The observation of Delpino, mentioned on p. 141 of this volume, can likewise 
only be explained by reference to the visual power of insects, and I therefore repeat 
his description—On a meadow in Vallombrosa there were numerous plants of 
Bellis perennis and Anemone nemorosa, equally mixed, and distributed at about 
equal distances from one another. Delpino saw a bee collecting pollen zealously 
from Anemone. When flying from one flower to another it repeatedly made a 
mistake and went to flowers of Bellis, though on reaching these recognized its error, 
and at once flew on again. 
Plateau has given a very one-sided interpretation to his experiments, without 
regard to the earlier observations of other investigators. For instance, he quite over- 
looks the experiments of Forel, who proved that blinded insects could not recognize 
the part of a flower on which they wished to settle, while others from which he had 
removed the antennae—which bear the olfactory organs—flew with certainty from 
flower to flower. 
Plateau further entirely ignores the results of the observations of Herrhann 
Miiller, which have been fully confirmed by the statistical investigations of 
E. Loew, J. MacLeod, and myself. By these the following conclusions have been 
established :— 
1. Other things being equal, a flower is visited by insects in proportion to its 
conspicuousness. Among nearly allied species which agree closely in the form and 
colour of their flowers, and naturally also agree in their floral mechanisms, those 
which are most conspicuous receive the most numerous visits, while those which are 
least conspicuous have the smallest number of visitors’. 
2. In a number of cases odour has more to do with the attraction of insects 
than the size and colour of the corolla. ‘The richly scented flowers of Convolvulus 
arvensis, says Hermann Miiller (‘ Fertilisation,” p. 572), ‘are far more abundantly 
visited than the larger and more conspicuous but scentless flowers of C. sepcum ; 
the sweet-scented violet is much more visited than the larger, brightly coloured, but 
scentless pansy; the small, insignificant, but strongly perfumed flowers of Lepedium 
sativum surpass in the abundance of their visitors the other more conspicuous but 
scentless Crucifers.’ 
3. Dull yellow flowers (Bupleurum, Anethum, Pastinaca, Alchemilla, and 
others) are not visited as a rule by beetles, while nearly related flowers that are 
white, or of some other conspicuous colour, attract these insects even when nectar- 
less (e.g. Helianthemum, Papaver, Genista). Reddish blue or violet flowers are 
preferred by bees, butterflies, and hover-flies, which are highly specialized visitors, 
while the insects that appear most frequently on white or yellow flowers have a short 
proboscis, and are unskilled visitors. Bees with a long proboscis (humble-bees) 
appear to be least dependent upon the colour of flowers. As Hermann Miller 
expresses himself (‘Alpenblumen,’ p. 496), ‘these—the most intelligent of flower 
1 H. Miiller (‘ Fertilisation,’ p. 570) gives as examples species of Ranunculus, Geranium, Malva, 
Polygonum, Stellaria, Cerastium, Epilobium, Rosa, Rubus, Veronica, Carduus, Hieracium, and the 
various flower-forms of Euphrasia officinalis, Rhinanthus Crista-galli, and Lysimachia vulgaris. 
