. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. ERICACEAE 47 529. Rhododendron L. Protandrous humble-bee flowers, usually brightly coloured; nectar secreted by an annular swelling at the base of the ovary. Kerner states that in many species the pollen-tetrads are bound together by threads of viscin. 1773. R. ferrugineum L. (Ricca, Atti See. ital. sc. nat., Milano, xiii; Herm. MuUer,' Alpenblumen,' pp. 378-9.)—In this species the abundant nectar collects in the base of the almost horizontal corolla-tube, e
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. ERICACEAE 47 529. Rhododendron L. Protandrous humble-bee flowers, usually brightly coloured; nectar secreted by an annular swelling at the base of the ovary. Kerner states that in many species the pollen-tetrads are bound together by threads of viscin. 1773. R. ferrugineum L. (Ricca, Atti See. ital. sc. nat., Milano, xiii; Herm. MuUer,' Alpenblumen,' pp. 378-9.)—In this species the abundant nectar collects in the base of the almost horizontal corolla-tube, especially in a slight pouch on the upper side of this. The erect hairs on the filaments serve as nectar-covers. In. Fig. 229. Rhododendron, L. (after Herm, Miiller), A. A just-openetl flower of/?, ferrugineitin, L. (natural size). B. A rather older llower of the same species. C. A younjr flower of R. hirsniitin, L. (in the male stage), after removal of the periantli and some of the stamens (>. 7). O. An older flower of the same species (in the female stage), treated similarly ( x 7}. //, nectar ; 7/, nectary; si, stigma. order to get at the nectar-bees and humble-bees must creep over the stamens and stigma into the base of the flower, and if this is in the first stage their under-side is dusted with pollen, which will be transferred to the stigmas of flowers in the second stage. As the longest stamens project beyond the stigma, automatic self-pollination is possible if insect-visits fail. Visitors.—The following were recorded by the observers, and for the localities stated.— Herm. Miiller (Alps), the honey-bee and 7 humble-bees, skg. legitimately and effecting cross-pollination; also, as unbidden guests, a beetle, 4 flies, an ant, and 9 Lepidoptera. Ricca (Alps), humble-bees up to a height of 2,200 m. MacLeod (Pyrenees), 3 humble-bees, Halictus, and a Muscid (Bot. Jaarb. Dodonaea, Ghent, iii, 1891. P- 373)- 1774. R. hirsutum L. (Herm. Miiller, op. cit.)—Hermann Mulle
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