464 THE FERTILISATION OF FLOWERS. [PART III. 
at the base form a delicate pollen-distributing apparatus. The 
fertilisers are flies and bees. 
2. Scrophularia has short, round, brownish flowers, with a 
widely open mouth and easily visible honey. The stigma ripens 
before the anthers, and both come in contact inferiorly with the 
insects. Wasps are the chief fertilisers. 
3. Digitalis, Antirrhinum, and Linaria have long and wide 
tubes, open in Digitalis and closed in the other two. The insect- 
visitor creeps entirely or almost entirely into the tube, and touches 
anthers and stigma with its back. The fertilising-agents are large 
bees. 
4. Euphrasia, Odontites, Rhinanthus, Melampyrum, and Pedicu- 
laris have narrow tubes which divide into an upper lip protecting 
the anthers, and a lower lip serving as a platform for imsects to 
alight on. They dust their insect-visitors with smooth, powdery 
pollen. The forms with shorter tubes are fertilised by bees and 
flies, those with longer tubes almost exclusively by humble-bees. 
On the Alps we have in addition TYozzia, fertilised by flies, 
Rhinanthus Alectorolophus by humble-bees and Lepidoptera, and 
R. alpinus by Lepidoptera (609). 
In almost all the Scrophularinez that we have considered, 
cross-fertilisation is effected by the stigma being touched before 
the stamens or pollen-apparatus by insect-visitors; but in some 
cases dichogamy also occurs. In default of insect-visits, self-fertili- 
sation takes place in most forms; and only in a few are insect- 
visits, and consequently cross-fertilisation, so far insured that self- 
fertilisation is never required and has become impossible. 
This family affords another instance of the association of certain 
colours with fertilisation by certain insects. In the section charac- 
terised by loose dry pollen, the lowest forms (Zozzta, Odontites 
lutea, and Euphrasia minima) are all yellow, while in the highest 
(Melampyrum, Pedicularis) red and purple colours appear. The 
uncommon colour of Serophularia must be referred to the peculiar 
taste of its visitors, the wasps. The colours of the genus Veronica, 
which is fertilised by flies, remain to be explained. Most species 
have light or dark blue flowers; those of V. urticifolia, and V. 
peregrina, L., are pink. In spite of its apparently simple flower, 
Veronica is by no means a primitive form among the Scrophu- 
larinee : the symmetrical flower, the specially differentiated 
nectary, the reduction of the sepals and petals to four, and of the 
stamens to two, are all characters widely removed from the 
primitive type. The short-tubed species of Veronica must be 
