44 THE FERTILISATION OF FLOWERS. [CHAP. 
spur. The bee on visiting the flower, alights on the 
median petal (MP), and its weight, by depressing 
the petals, probably forces the side of the spur (Sp) 
against the anther processes (Ap), the effect of which 
is to unlock the ring of anthers (A). The bee’s head 
also strikes against the stigma, which causes the loose 
dry pollen to fall on the bee’s face. On visiting 
another flower this pollen will be deposited on the 
under-surface of the stigma. It is remarkable that 
in this species the pollen is dry and loose, whilst in 
most entomophilous flowers it is sufficiently sticky to 
adhere to the anthers, but in this case the bee does 
not rub against the anther, therefore if the pollen 
wete not loose and dry, fertilisation could not take 
place. 
In the pretty little Milkwort (Polygala vulgaris) 
again, we have a different arrangement. The petals 
form a tube to which the stamens are attached in two 
bundles near the top. Below these is the stigma, and 
behind it a viscid disc. The proboscis of an insect | 
pushed down this tube in search of honey comes in 
contact with the viscid disc, and is thus rendered 
adhesive. When it is withdrawn it touches against 
the anthers and carries off some of the pollen to be 
deposited on another flower. 
In the Mallows (J/alva) we have good evidence 
of the truth of the theory that the object of colour 
in flowers is to attract insects. We have two species 
of Mallows growing in the same locality, Malva 
sylvestris and M. rotundifolia, Sylvestris is fertilised 
by insects, rotundifolia fertilises itself, and is seldom 
visited by insects. Sylvestvis has large conspicuous 
