ERICACEAE 



37 



■white flowers, the corolla-lobes of which are of a purple-red colour (op. cit., p. 49). 

 Nathorst found it in full bloom in Spitzbergen (1.8. '68) (Andersson and Hesselman, 

 op. cit., p. 12). 



3. Tribe Ericeae. 



523. Calluna Salisb. 



Feebly protandrous, pinkish-red, rarely white flowers, aggregated into racemes ; 

 with concealed nectar, secreted in the base of the flower by eight little swellings 

 alternating with the filaments. 



1762. C. vulgaris Salisb. (=Erica vulgaris Z.). (Sprengel, ' Entd. Geh.,' 

 p. 230; Herm. IMuUer, 'Fertilisation,' pp. 377-80, ' Alpenblumen,' p. 382, ' Weit. 

 Beob.,' Ill, p. 67 ; Lindman, ' Bidrag till Kanned. om Skandin. Fjellvaxt. Blomn. o. 

 Befruki.' ; Verhoeff, ' Bl. u. Insekt. a. d. Ins. Norderney'; de Vries, Ned. Kruidk. 

 Arch., Nijmegen, 2. Ser., 2. Deel, 1875 ; IMacLeod, Bot. Jaarb. Dodonaea, Ghent, iii, 

 1891, V, 1893; Knuth, ' Bl. u. Insekt. a. d. nordfr. Ins.,' pp. loi, 163, 'Weit. Beob. 

 ii. Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 227, 238 ; Kerner, ' Nat. Hist. PI.,' Eng. Ed. i, 

 II, p. 139; Loew, • Bliitenbiol. 

 Floristik,' p. 390 ; Warnstorf, 

 Verh. bot. Ver., Berlin, xxxviii, 

 1896. ) — The attraction of i nsects 

 effecting cross-pollination is 

 brought about by the enlarged 

 red, rarely white calyx, the 

 aggregation of the flowers into 

 dense unilateral racemes, and 

 last, but not least, by the asso- 

 ciation together of vast numbers 

 of plants. 



Hermann Miiller describes 

 the flowers as feebly protan- 

 drous, with small bells 2-3 mm. in length. The stamens and pistil are so bent up 

 in the almost horizontal blossoms that the nectar is conveniently accessible from 

 below. The larger insects (bees and humble-bees) hang on to the flowers, pulling 

 them down by their weight, and suck from below ; the smaller ones, on the contrary, 

 push their head or proboscis into the flowers from the front in order to secure nectar, 

 and in doing so get dusted with pollen from above. 



The anthers dehisce in the bud, and their rough appendages, beset with stiff' 

 erect hairs, so block the outer part of the flower that a proboscis probing for nectar 

 is obliged to strike against them, when pollen is showered down. The four-lobed 

 stigma projects considerably beyond the tips of the anthers, and does not usually 

 become receptive until all the pollen is shed, though some of this may previously 

 adhere to it. Crossing is therefore ensured by insect-visits, and automatic self- 

 pollination is excluded. 



Kerner states that the flowers are only at first adapted to insect-pollination, 

 becoming anemophilous later on. The secretion of nectar then ceases, the filaments 



Fig. .124. Calhaia vulgaris, Salisb. (after Herm. Muller)- 

 (1) Older flower, seen almost directly from below. {2) Younger 

 do., after removal of half the calyx and corolla, seen from the side. 

 (3) A stamen. a, sepals; b, j)etals; c, appendages of the anthers; 

 d^ nectary \ c, opt-ninj^s of the anthers ;y", filaments ; ^, style. 



