448 ANGIOSPERMAE—DICOTYLEDONES 



in a state of downward and the filament in a state of upward tension, an insect 

 alighting upon the staminode in order to reach the pseudo-nectaries {vide supra), 

 will cause these opposed strains to become effective. The spoon will suddenly bend 

 downwards, while the stamen immediately above it will explode upwards, at the 

 same time applying its pollen to the under-side of the visitor's body. The stamen 

 afterwards bends out of the flower, while the style goes on growing, and projects 

 from the flower to serve as an alighting-place. Automatic self-pollination is excluded. 

 Visitors. — Herm. Mtiller frequently observed the house-fly (Musca domestica 

 L.) and the common gnat (Culex pipiens L.) effect pollination in his room, and the 

 honey-bee do so at an open window ('Fertilisation,' p. 265). 



1055. L. racemosa Cav. — According to Ogle's account (Pop. Sci. Rev., London, 

 viii, 1869, p. 271), the flower mechanism of this species is the same as that of 

 L. coronata. 



1056. L. miniata DC. (Hildebrand, op. cit., xxiv, 1866, pp. 478-9.) — In this 

 species the fertile stamen is not explosive, and lies above the spoon-shaped staminode. 



302. Oenothera L. 



Protandrous lepidopterid flowers. Honey is secreted by and concealed in the 

 base of the calyx-tube. Kerner states that the peduncle is curved so as to make 

 the entrance to the flower lateral. He also describes the pollen-grains as being 

 bound together by threads of viscin. Many of the species are night flowerers 

 (vide infra). 



1057. O. biennis L. (Sprengel, 'Entd. Geh.,' pp. 217-23; Herm. Muller, 

 'Fertilisation,' p. 264 ; Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, II ; Knuth, 'Bl. u. Insekt. 

 a. d. nordfr. Ins.,' p. 151, 'Bloemenbiol. Bijdragen.') — Sprengel long 9.go thoroughly 

 described the flower mechanism of this species, which is native to Virginia. The 

 large bright yellow flowers are devoid of nectar-guides. They open in the evening, 

 and are then most fragrant, and would therefore appear to be especially adapted 

 to crepuscular and nocturnal Lepidoptera. They are, however, owing to their 

 bright yellow petals, also conspicuous during the day, when they are visited by 

 long-tongued bees, and must consequently be placed in the transition class, LmH. 

 The secretion of the smooth, yellow nectary in the base of the calyx-tube is 

 protected by fine woolly hairs. It flows into the upper naked part of the tube, 

 and adheres to the style, which is here pressed against the lower wall of the 

 tube. The individual flowers remain in bloom for two nights. Kerner says that 

 they open shortly before 6 p.m., and close twenty-four hours later. When the 

 flower opens, the anthers shed their pollen, but at this stage the four stigmas are 

 still apposed. On the morning of the second day the stigmas begin to diverge, 

 and are fully developed the second night, while the stamens are now shrivelled. 

 Kerner says that the edge of the corolla does not serve as an alighting-place for 

 insect visitors, but is only attractive. When a visitor inserts its proboscis into 

 a flower, it touches the anthers with its head, and at the beginning of anthesis 

 the stigmas, owing to a lateral curvature of the style, are out of the line of access 

 to the nectar. But, according to Kerner's account, the style straightens half an 

 hour later, and the stigmas spread out, so that crossing may be eff"ected by insects 



