58 ANGIOSPERMAE DICOTYLEDON ES 



Automatic self-pollination is almost unavoidable in (c) ; pollen can easily fall 

 from the anthers on the stigma in (b) ; autogamy sometimes takes place in (a) by 

 bending down of the style. 



MacLeod also observed numerous flowers with sterile stamens, so that there 

 is a tendency to gynodioecism. 



Visitors. The following were recorded by the observers, and for the localities 

 stated. 



Knuth (Amrum), only a few minute Muscids, and a bug (Lygus pratensis i^.) 

 obviously not adapted to the size and mechanism of the flowers, for a proboscis 

 5-6 mm. long is required to reach the nectar: (Sylt), the honey-bee, in enormous 

 numbers, skg., the humble-bee Bombus terrester Z., do., and the hover-fly Meli- 

 threptus nitidicollis Zett., do. : (Langeness in the Hallige), medium-sized Diptera. 

 Willis (neighbourhood of the south coast of Scotland), a beetle (Meligethes sp., po- 

 dvg.) and a humble-bee (Bombus hortorum Z., skg.) ('Fls. and Insects in Gt. Britain,' 

 Part I). Scott-Elliot (Dumfriesshire), a humble-bee and the beetle Meligethes (' Flora 

 of Dumfriesshire,' p. 142). 



LXIV. ORDER PRIMULACEAE VENT. 



Literature. Herm. Miiller, 'Alpenblumen,' pp. 373-4; Knuth, 'Bl. u. Insekt. 

 a. d. nordfr. Ins.,' p. 120, 'Grundriss d. Bliitenbiol.,' p. 86. 



The brightly coloured corolla serves to attract insects. Numerous gradations are 

 found between open nectarless flowers and such as are adapted by the way in which 

 nectar is concealed and their entire mechanism to a restricted circle of long-tongued 

 and industrious insects (bees, Lepidoptera). The flowers belong to the following 

 classes : Po : Trientalis, Lysimachia, Anagallis, Centunculus, Samolus (with pseudo- 

 nectaries). C : Glaux (?), Hottonia, Androsace, Soldanella pusilla Bawng., var. 

 inclmata Hb. : Soldanella pusilla Bamng., var. pendula, S. alpina. HbLb : Primula 

 elatior Hill, P. officinalis Jacq., P. vulgaris Huds. Lb : Primula integrifolia Z., 

 P. farinosa Z., P. viscosa AIL, P. longifolia All. (diurnal hawk-moth flowers). The 

 species of Hottonia and Primula are usually dimorphous. 



538. Trientalis Rupp. 



Open protogynous pollen flowers, sometimes, according to Schulz, varying 

 to homogamous. The thick fleshy ring which bears the stamens and surrounds the 

 ovary is, however, so juicy that Hermann Muller suggests many visitors may bore it 

 to get the sap. 



1793. T. europaea L. (Herm. Muller, ' Weit. Beob.,' Ill, pp. 65-6 ; Schulz, 

 'Beitrage,' I, p. 88.) Hermann Muller says that the white petals of this species 

 spread out into a flat star 12-15 ni"i' broad. The stamens are directed obliquely 

 upwards and outwards, and their anthers as a rule at first remain closed, while the 

 stigma is at the same level and receptive when the flower opens. The flowers 

 examined by Schulz in the Riesengebirge were either homogamous or very feebly 

 protogynous. The anthers dehisce above and internally, so that an insect when 

 pushing its head into the base of the flower must touch the pollen with one side 



