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 Muller says that 

 the flower mechanism of this species completely agrees with that of R. ferrugineum. 

 Hansgirg noticed the occurrence of pseudo-cleistogamy. 



