32 ANGIOSPERMAE—DICOTYLEDONES 



of them is produced into a pair of tubes as long as itself, open at the tip, and closely 

 embracing the style. In order to get at the nectar, bees must climb on to the flowers 

 from below, and thrust their proboscis between the tubular prolongation of the anthers, 

 from which pollen falls upon their heads. Since the stigma is the part projecting 

 furthest from the corolla, it is first touched by the pollen-covered heads of bee visitors, 

 so that crossing must necessarily take place. Lindman says that automatic self- 

 pollination is not assured in the \&r.pusilla Rupr., owing to the great distance between 

 stigma and anthers, but Warming is of opinion that in Greenland it may take place in 

 the bud, for very numerous fruits are set there. Warnstorf describes the pollen-grains 

 as white in colour, and up to 50 /u. in diameter. 



Visitors. — In spite of long and careful watching I have never been able to 

 observe any, nor was Herm. Miiller more successful. The latter adds that though 

 honey-bees quench their thirst with the water which permeates the masses of 

 Sphagnum in the immediate neighbourhood of the flowers, they do not trouble 

 about these. He also correlates the very long time for which anthesis lasts with 

 the sparsity of insect-visits. Scott-Elliot observed 2 Muscids, which were obviously 

 useless guests ('Flora of Dumfriesshire,' p. in). 



LX. ORDER ERICACEAE LINDL. 

 (including Rhodoraceae Klotsch, and Pyrolaceae Lindl). 



Literature. — Knuth, ' Grundriss d. Blutenbiol.,' p. 70 ; Drude, in Engler u. 

 Prantl., ' D. nat. Pflanzenfam.,' IV, i, p. 25. 



Flowers usually in racemes, rarely (Andromeda) in umbels : nectar concealed in 

 the base of the corolla. The anthers generally possess two processes which reach the 

 corolla, are struck by insect visitors, and serve as levers for scattering the pollen, 

 which consists in many species of loosely connected tetrads. 



1. Tribe Arbuteae. 



519. Arctostaphylos Adans. 



Homogamous or feebly protogynous humble-bee flowers, with nectar secreted by 

 a fleshy ring surrounding the ovary. Kerner states that automatic self-poUination 

 can ultimately take place as in Vaccinium. 



1755' A. Uva-ursi Spreng. (=A. officinalis Wimvi. el Grab., and Arbutus 

 Uva-ursi Z.). (Herm. Miiller, ' Alpenblumen,' pp. 385-8.) — The pendulous flowers 

 of this species are arranged in short terminal racemes, and the corollas are almost 

 conical bells. The nectar does not remain adhering to the nectary, but is sheltered 

 in ten pits which surround it at the base of the corolla. It is prevented from running 

 away by the dense hairy covering of the filaments and inner surface of the corolla. 

 It is also protected against unbidden guests by long erect hairs at the opening of the 

 corolla. The ten filaments are narrow at their bases, and then enlarge very quickly 

 to form a ring surrounding the ovary, afterwards narrowing again, but continuing 

 to remain apposed to the ovary for some distance. Their ends project beyond 



