316 The Romance of Wild Flowers 
central. Honey is poured forth from the inner 
surface of the lower parts of the flower, and flows all 
around the ovary, yet it can be reached only from 
the sepals, and the insect must have a long tongue 
to obtain it, although he can push his head some dis- 
tance between style and sepal. 
On examining a number of Flag-plants, it will be 
seen that there are two types of flower. In one the 
style hes close upon the sepal, leaving no room for a 
bee to crawl between; in the other form there is 
sufficient room for a humble-bee. Now, these two 
conditions have evidently arisen to adapt the flower 
for fertilisation by two different insects. Both forms 
are much visited by the Long-tongued Hover-fly 
(Rhingia rostrata), and the more roomy flowers 
enable it to obtain honey without fertilising in return ; 
not only so, but before it leaves the flower it reaches 
up to the anther and feeds on the pollen also. What 
we may call the bee-form therefore loses by the 
patronage of Rhingia and gains nothing in return. 
But there are several species of Humble-bees (Bombus 
agrorum, B. hortoruwm, and B. derhamellus) that also 
frequent these flowers, and these on pushing between 
style and sepal at first rub their backs against the 
stigmatic scale and fertilise it with pollen they may 
have brought from a previously visited Flag; then 
they rub their hairy backs against the anther, and 
take up a fresh supply of pollen before they reach 
the honey. In retreating from the flower they do 
not retrace their course, but crawl sideways from 
beneath the style without touching the stigma. In 
the fly-form of flower Rhingia goes through a process 
similar to that of the bee in the other form, but when 
