590 THE FERTILISATION OF FLOWERS. [PART IV. 
visitor always comes in contact first with the stigma and after- 
wards with the anthers (Anthericum, Convallaria majalis, Lonicera 
Caprifolium, many Labiatze, etc.), or if in each flower any part 
of the proboscis, body, or head of the insect touches the stigma 
while at the same time the opposite side touches the anthers 
(Myosotis, Omphalodes, Ribes nigrum, Berberis, Cruciferae, etc.). 
When the flowers are not all alike, that is to say in dimorphic 
(Primula, Hottonia, Pulmonaria, Polygonum fagopyrum) or tri- 
morphic (Lythrwm) plants, cross-fertilisation is insured if the insects 
touch the anthers and stigma with different parts of their bodies, 
but touch the stigma with that part which touched the anthers in 
a previous flower. 
The mechanisms for applying pollen to a particular part of the 
insect are astonishingly various; from the nature of the case they 
can be the more easily attained the more the circle of visitors is 
restricted to a few definite forms by concealment of the honey. 
As examples of these multitudinous arrangements we may recall 
the flowers of Ericaceze, Scrophulariacee, Boraginee, and Galanthus, 
in which pollen is sifted on to the insect; the infinite number of 
devices in Orchidew ; and the somewhat similar mechanism of 
Asclepiadaceze ; the flowers of Papilionaceze, Fumariaces, and 
of Lopezia, in all of which the insect involuntarily opens the 
pollen-receptacle and dusts itself ventrally with pollen; Salvia, 
in which the mechanism is reversed and the insect’s back receives 
the pollen; lastly, the simple device of the flexible stamens in 
Veronica Chamedrys and Circa. 
The mechanisms which have been discussed in this book are 
only an infinitesimal fraction of the vast variety that exists. They 
arose quite independently and at various times in the various 
divisions of those Phanerogams which had become entomophilous 
and monoclinic. They have in general become developed only 
where increasing conspicuousness and a large supply of food material 
attracted so many insects that the capability for self-fertilisation be- 
came unnecessary ; on the other hand, where insect-visits remained 
few, the power of self-fertilisation (which began with the appearance 
of hermaphroditism) was retained. Where cross-fertilisation that 
1 The mechanisms for insuring cross-fertilisation in Umbellifere and in Com- 
posite have been inherited from the ancestors of the order; those in the various 
species of Aquilegia, Delphinium, Linaria, and Pedicularis, from the ancestor of the 
genus ; those in Polygonwm fagopyrum, P. Bistorta, and Lonicera Caprifolium, from 
the ancestor of the species ; while the different forms of flowers in Rhinanthus erista- 
galli, Veronica spicata, Odontites serotina, -Euphrasia officinalis, and Lysimachia 
vulgaris, give us examples of various floral characters being evolved within the bounds 
of one and the same species, 
