This section is from the book "On British Wild Flowers Considered In Relation To Insects", by John Lubbock. Also available from Amazon: Nature Series On British Wild Flowers Considered In Relation To Insects.
This order is represented in Britain by eight genera: Primula, Lysimachia, Trientalis, Glaux, Anagallis, Centunculus, Samolus, and Hottonia. Cyclamen also grows wild in some places, but is not a true native.
I have already referred to the genus Primula in the introductory chapter (ante, p. 33). The majority of the species are dimorphous, but not all (Scott, "Proc. Linn Soc," vol. viii. 1864). In Primula Stricta, according to Axell ("Om Anord. for de Vax Befrucktning"), when the flowers first open, the anthers are already mature, and are attached to the tube of the corolla, some distance above the as yet immature stigma. Gradually, however, the pistil elongates, bringing the stigma to the same height as the anthers.
Hottonia palnstris, though so unlike Primula in habit and appearance, is also dimorphous, and agrees with the former genus very nearly in the relative positions of the stamens and pistil in the two forms. The difference was noticed by Sprengel, who says (p. 103), "I think this is not accidental, but a provision of nature, though I am not in a position to point out the advantage of it."
Lysimacliia vulgaris produces no honey. In this species Muller has observed the existence of two extremes (connected, however, by intermediate forms); one, more conspicuous, which rarely or never fertilises itself; the other less conspicuous frequenting shady places, and habitually self-fertile.
Of the genus Anagallis (the Pimpernel) we have, according to Bentham, two species only, A. arvensis and A. tenella. The former, however, contains two well-marked varieties, one blue and the other red, which do not cross, and are considered by some botanists as distinct species, under the names of A. caerulea, and A, arvensis. Whether it may be more convenient to treat them as true species or as mere varieties, it must at least be admitted that they differ considerably.
Not only are they of different colours, the one blue, the other red, but A. caemlea is very decidedly smaller. The stamens and pistil ripen simultaneously. The flowers contain no honey, and partially close about three o'clock in the afternoon.
The flowers are seldom visited by insects, and it would appear that they generally fertilise themselves. This is said to be the case also with Centunculus minimus.