316 
DARWINISM 
CHAP. 
debted to the exact and long-continued researches of Professor 
Hermann Muller. 
Summary of Additional Facts bearing 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 Muller 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, 
paeonies, 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, I). 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 
