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a. d. nordfr agrorum F Alfken Alpenblumen Alps Andrena anthers anthers dehisce anthesis Apidae Apis mellifica autogamy automatic self-pollination bees beetles Beitrage Beob Berlin Botanic Garden Bliitenbiol Bloemenbiol Bombus agrorum Bombus terrester Budd calyx carina carpels Coleoptera colour corolla cylindricus dehisce diameter Diptera Dodonaea Dumfriesshire effect cross-pollination Eristalis arbustorum female flowers Fertilisation filaments flies Flora of Dumfriesshire florets flower mechanism freq Ghent Halictus Herm Hermann Muller hermaphrodite flowers homogamous honey-bee hortorum hover-flies humble-bees Hymenoptera inner insect visitors insect-visits Jaarb Kerner Kiel Kirchner Knuth lapidarius Lepidoptera Loew long stamens MacLeod male flowers mature Meligethes Miiller Muscidae nect-lkg nectar Nitidulidae numerous observed the following Osmia petals pistil plant po-cltg po-dvg pollen pollen-grains proboscis protandrous protogynous Rhopalocera Schenck Schulz Scop Scott-Elliot secreted sepals short stamens short-tongued Sphegidae Spitzbergen stamens stigma Stuttgart style Syritta pipiens Syrphidae Syrphus tenax Thuringia Tyrol V1s1tors.—Herm V1s1tors.—Loew observed Warnstorf yellow
Page 45 - ... hollow cone to the front, and as they expand and turn up anteriorly, they afford a convenient approach to the proboscis of a humble-bee, and also direct it with certainty to the nectar receptacle. These anterior parts of the upper petals separate on slight pressure, so that the head of a humble-bee can be entirely thrust between them, thus diminishing the distance to the nectar by 6 to 7 mm.
Page 436 - His experiments with this loosestrife also demonstrated that "reproductive organs, when of different length, behave to one another like different species of the same genus in regard both to direct productiveness and the character of the offspring ; and that consequently mutual barrenness, which was once thought conclusive proof of difference of species, is worthless as such, and the last barrier that was raised between species and varieties is broken down.
Page 44 - Delphinium datum, is described by Knuth as follows : 177 masterly fashion, the spur of the sepal not only serves to protect the nectar, but also compels the bumble-bees that alight in search of nectar to do so in the only way that effects pollination. The hollow, sharply conical end of the posterior process of each upper petal secretes nectar, getting so full of it that some enters the semiconical cavity of this process, which is open on its inner side.
Page 661 - ... Milwaukee, Wisconsin. Blooming freely, August 12, 1927. No honey bees. Centaurea L. Star Thistle Herbs with alternate leaves and single heads. Heads manyflowered. Flowers usually purplish, tubular, marginal flowers longer than neutral. Disc florets hermaphrodite. Filaments irritable to touch. Knuth says, "Kerner states that the pollen is concealed in the anther-cylinder until insects visit the florets, being thus protected from rain and dew. When the proboscis of a nectar-seeking insect stimulates...
Page 324 - ... The wings are violet in color and the keel is whitish with a blue tip. The keel and wings are united in such a way that to secure pollination the insect must light upon the keel, which is then pressed down and the stamens come in contact with the thorax of the bee. Knuth puts it in the following way, "The posterior angles of the carina are drawn out into processes which lie upon the sexual column. There are also finger-shaped alar processes, running backwards parallel to each other. The upper...
Page 276 - ... speak, fired off. He states that the upper surfaces of the alae are beset with papillae, serving as footholds to insect visitors. There is also a marginal row of papillae on either side of the vexillum's inner surface, to which long-legged insects would appear to cling. The stigma remains unreceptive until its papillae have been subjected to friction. By covering a number of inflorescences with nets, in order to keep away insects, Burkill was able to confirm the conclusion at which Urban had...
Page 260 - The carina is a protective structure, sheltering the stamens and pistils and keeping away unbidden guests (Lepidoptera and flies). When all ten filaments cohere, the flowers afford only pollen, but when the upper one is free, there is a slit on either side of it, leading to the nectar secreted inside the bases of the stamens. The closed or split cylinder formed by the filaments envelops the pistil, of which the style is usually upwardly curved at the tip, and projects somewhat beyond the anthers,...
Page 570 - ... is closely surrounded in the bud by an involucre usually made up of several series of bracts. This subsequently serves as an adequate protection against creeping animals, as well as to hold the inflorescence together. 672 corollas, or by the production of a limb of each into a long outer lobe. ' ' Nectar is secreted by a ridge surrounding the base of the style. It is so abundant as to rise in the corolla-tube and is protected from rain by the filaments which converge above it. It is accessible...
Page 44 - ... masterly fashion, the spur of the sepal not only serves to protect the nectar, but also compels the bumble-bees that alight in search of nectar to do so in the only way that effects pollination. The hollow, sharply conical end of the posterior process of each upper petal secretes nectar, getting so full of it that some enters the semiconical cavity of this process, which is open on its inner side. As the two spurs are closely apposed they together form a hollow cone, splitting at the end into...