. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. RHAMNEAE 247 Visitors.—At Kiel I only saw a hover-fly (Eristalis nemorum Z.), skg. Hoffer observed Bombus hypnorum L. 5 in Steiermark. 617. R. pumila L. (Herm. Muller, ' Alpenblumen,' pp. 169-71.)—The small flowers of this species—which Kerner describes as possessing an odour of honey— are said by Muller to be usually hermaphrodite, while Koch (' Synopsis') describes them as dioecious-polygamous. Cross-pollination is favoured in the hermaphrodite flowers owi
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. RHAMNEAE 247 Visitors.—At Kiel I only saw a hover-fly (Eristalis nemorum Z.), skg. Hoffer observed Bombus hypnorum L. 5 in Steiermark. 617. R. pumila L. (Herm. Muller, ' Alpenblumen,' pp. 169-71.)—The small flowers of this species—which Kerner describes as possessing an odour of honey— are said by Muller to be usually hermaphrodite, while Koch (' Synopsis') describes them as dioecious-polygamous. Cross-pollination is favoured in the hermaphrodite flowers owing to the fact that the stamens and stigmas are on opposite sides of the nectar. Visitors.—Herm. Muller observed Hymenoptera (Chrysididae, Formicidae), beetles, and Diptera (Muscidae, Empidae, Syrphidae), in the Alps. 6x8. R. saxatilis L.—Kerner describes this species as dioecious, with pseudo- hermaphrodite pollen-flowers and fruiting-flowers. 619. R. Frangula L. (=Frangula Alnus Mill). (Herm. Muller, ' Fertilisation,' pp. 163-4, 'Weit. II, p. 212; Kirchner, 'Flora v. Stuttgart,' pp. 363-4; Warnstorf, Verb. bot. Ver., Berlin, xxxviii, 1896; Schuiz, 'Bei- trage,' I, p. 31, II, p. 61; Knuth, ' Bloemenbiol. Bijdragen.')—The in- conspicuous greenish-white herma- phrodite flowers of this species, according to the investigations of Hermann Muller and A. Schultz, are protandrous to a less (Thuringia) or greater (Westphalia, South Tyrol) degree. The cup-shaped calyx is also a hemispherical nectary. Between the five triangular whitish tips of the sepals, are five small white bifid petals, which almost cover the five inwardly curved introrse stamens. In the base of the calyx lies the short-styled pistil, the bilobed stigma of which is at a lower level than the anthers. At the time when the latter are ripe the stigma is still ill-developed. Insect visitors usually effect cross-pollination while sucking nectar, since they touch the anthers with one side of their body
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