PRIMULACEAE 59 



of this and the stigma with the other. When several blossoms are visited successively 

 crossing must regularly be brought about. 



In the course of anthesis the style elongates to some extent, so that the stigma, 

 at first on the same level as the anthers, ultimately projects beyond them. The flower 

 closes again when it withers, pressing the stamens against the style, so that some 

 pollen can now easily fall on the stigma, or this may come into contact with some of 

 the grains that have dropped on the petals. 



The species is represented in the Arctic regions by a variety different in some 

 respects, i. e. arcHca Fisch. 



Visitors. Herm. Miiller only observed the beetle Meligethes. 



539- Lysimachia L. 



Homogamous yellow pollen flowers. 



1794. L. vulgaris L. (Herm. Miiller, ' Fertilisation,' pp. 389-90, ' Weit. Beob.,' 

 Ill, p. 65; MacLeod, Bot. Jaarb. Dodonaea, Ghent, v, 1893, pp. 443-4; Warnstorf, 

 Verb. bot. Ver., Berlin, xxxviii, 1896; Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 120-1, 

 ' Weit. Beob. u. Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 229-30, ' Bloemenbiol. Bijdragen ' ; 

 Kirchner, 'Flora v. Stuttgart,' pp. 531-2.) The golden-yellow flowers of this species 

 exist in three different oecological forms. 



(a) aprica Knuth: corolla-lobes about 12 mm. long and 6 mm. broad, golden- 

 yellow in colour with red bases, tips reflexed ; filaments red towards their tips ; 

 style projecting a few millimetres beyond the two longest stamens, thus ensuring 

 crossing by insect visitors, and rendering automatic self-pollination difficult. Grows 

 in sunny stations on the mainland (but not in the North Frisian Islands). 



(3) tmihrosa Knuth : corolla-lobes about 10 mm. long and 6 mm. broad, 

 bright-yellow in colour, directed obliquely upwards, tips not reflexed ; filaments 

 greenish-yellow; style as long as the two longer stamens, so that automatic self- 

 pollination is inevitable failing insect-visits. Grows in shady stations. 



(c) intermedia Knuth : corolla-lobes 10 mm. long and 5 mm. broad, distant, 

 bright-yellow in colour, sometimes reddish at the base ; filaments usually reddish ; 

 style somewhat longer than the two longest stamens, so that automatic self- 

 pollination takes place more easily than in (a), and with greater difficulty than in (b). 

 Grows in stations of intermediate character, e. g. the sunny edges of ditches. 

 Approximates sometimes to one, sometimes to the other of the well-defined varieties 

 (a) and (b). 



Warnstorf describes the pollen-grains as yellow in colour, ellipsoidal, coarsely 

 tuberculate, about 37 /* long and 23 /x broad. 



Visitors. The most important is the bee Macropis labiata Pz., the presence of 

 which in a district appears to be related to that of this species (Ducke also observed 

 at Trieste the rare species IMacropis frivaldskyi Mocs.). In the North Frisian Islands, 

 which are otherwise rather poor in insects, I found considerable numbers of this bee 

 on the flowers, its hind-legs laden with enormous balls of pollen. In the East Frisian 

 Islands, on the other hand, where this plant is absent, the bee has not been observed, 

 although a pretty complete entomological survey has been made. The same bee has 



