316 DARWINISM chap. 



debted to the exact and long-continued researches of Professor 

 Hermann Muller. 



Summary of Additional Facts hearing on Insect Fertilisation. 



1. That the size and colour of a flower are important 

 factors in determining the visits of insects, is shown by the 

 general fact of more insects visiting conspicuous than incon- 

 spicuous flowers. As a single instance, the handsome Geranium 

 palustre was observed by Professor Miiller to be visited by 

 sixteen different species of insects, the equally showy G-. 

 pratense by thirteen species, while the smaller and much 

 less conspicuous G-. molle was visited by eight species, and 

 G. pusillum by only one. In many cases, however, a flower 

 may be very attractive to only a few species of insects ; and 

 Professor Muller states, as the result of many years' assiduous 

 observation, that "a species of flower is the more visited by 

 insects the more conspicuous it is." 



2. Sweet odour is usually supplementary to the attraction of 

 colour. Thus it is rarely present in the largest and most gaudily 

 coloured flowers which inhabit open places, such as poppies, 

 pseonies, sunflowers, and many others; while it is often the 

 accompaniment of inconspicuous flowers, as the mignonette ; of 

 such as grow in shady places, as the violet and primrose ; and 

 especially of white or yellowish flowers, as the white jasmine, 

 clematis, stephanotis, etc. 



3. White flowers are often fertilised by moths, and very 

 frequently give out their scent only by night, as in our butterfly- 

 orchis (Habenaria chlorantha) ; and they sometimes open only at 

 night, as do many of the evening primroses and other flowers. 

 These flowers are often long tubed in accordance with the 

 length of the moths' probosces, as in the genus Pancratium, 

 our butterfly orchis, white jasmine, and a host of others. 



4. Bright red flowers are very attractive to butterflies, and 

 are sometimes specially adapted to be fertilised by them, as 

 in many pinks (Dianthus deltoides, D. superbus, D. atrorubens), 

 the corn-cockle (Lychnis Githago), and many others. Blue 

 flowers are especially attractive to bees and other hymenoptera 

 (though they frequent flowers of all colours), no less than sixty- 

 seven species of this order having been observed to visit the 

 common "sheep's -bit" (Jasione montana). Dull yellow or 



