40 



ANGIOSPERMAEDICOTYLEDONES 



524. Erica L. 



The species of this genus belong to flower classes H, L, LH, C, and An. 



1763. E. Tetralix L. (Herm. Miiller, 'Fertilisation,' pp. 376-7, ' Weit. Beob.,' 

 Ill, p. 67; MacLeod, Bot. Jaarb. Dodonaea, Ghent, v, 1893, PP- 45-! > Schulz, 

 ' Beitrage'; Knuth, 'Bl. u. Insekt. a, d. nordfr. Ins.,' p. 161, 'Weit. Beob. u. Bl. u. 

 Insekt. a. d. nordfr. Ins.,' 238.) This species belongs to the class of bee flowers. 

 The pendulous red flower bells, aggregated into capitulo-umbellate inflorescences, 

 make the plant very conspicuous. Hermann Miiller says that their mechanism 

 agrees with those of Vaccinium Myrtillus and V. uliginosum. The flower bell is 



7 mm. long, and its central part 4 mm. broad. 

 The ovary is sessile in the bottom of the flower, 

 and its base is surrounded by a blackish annular 

 nectary, the secretion of which accumulates where 

 it is formed. The blackish sticky stigma occupies 

 the narrow (only 2 mm.) opening of the corolla, 

 or even projects from it, so that an insect visitor 

 hanging on to the blossom and probing for nectar 

 must first touch this, effecting cross-pollination if 

 another flower has previously been visited. At 

 the same time the insect's proboscis is moistened 

 with the sticky stigmatic fluid, and made ready 

 to receive a fresh supply of pollen. The down- 

 wardly directed anther-pores are situated some- 

 what above the stigma, and the pairs of long 

 pointed thorn-like anther-processes stretch as far 

 as the wall of the bell. Immediately after the 

 proboscis of a nectar-seeking insect has touched 

 the stigma, it strikes against some of these pro- 

 cesses, and some of the dry powdery pollen falls 

 from the anther-pores upon the front part of its 

 head, adhering to the part previously made sticky 

 with stigmatic fluid. When the next flower is 

 visited crossing must take place, the head of the 

 insect being at the same time sprinkled with 

 more pollen. Failing insect-visits, automatic self-pollination is eff'ected by fall of 

 pollen on the edge of the stigma. I have not myself determined whether the 

 flowers become anemophilous towards the end of anthesis. 



A proboscis 7 mm. long is required to obtain the nectar, and as that of the 

 honey-bee is only 6 mm. in length, this zealous visitor is unable to suck legitimately. 

 It therefore perforates the bell somewhere about the middle, and steals the nectar 

 through the aperture. Hermann Muller, however, observed it sucking autumn 

 flowers in the normal fashion, and he thinks that these are perhaps a little smaller 

 than those developed in the warmer part of the year, so that the proboscis of the 

 honey-bee may be long enough to get at the nectar legitimately {c/. my remark 

 below). 



Fig. 225. Erica Tetralix, L. (after 

 Herm. Miiller). A flower from which the 

 front half of the corolla has been removed, 

 a, calyx ; i, corolla ; r, reflexed limb of the 

 same ; d, stamens (partly displaced) ; , the 

 downwardly directed openings of the an- 

 thers ; f, appendages of the anthers, which 

 are [struck against by the proboscis of in- 

 sects probing the flower; g, nectary; h, 

 ovary ; i, style ; k, stigma. 



