THE DICOTYLEDONES 1867 



so that only the proboscis of a bee can enter and reach the base of the flower. 

 The capitate stigma projects a httle from the mouth of the flower in a 

 position suitable for receiving pollen before the insect reaches the anthers, 

 which cluster around the style inside the bell-shaped flower. Each anther 

 has two long basal appendages, which diverge outwards and touch the 

 inner wall of the corolla. When the bee's proboscis touches them it causes 

 the dry pollen in the anthers to fall out on to the insect's head. Nectar is 

 secreted by a white annular swelling at the base of the style. As in previous 

 examples, should cross-pollination fail, self-pollination is possible by the 

 pollen falling on the stigma, since the flowers are pendulous. 



Fig. 1774- — Vacciniuni 

 myrtilhis. Flower in 

 longitudinal section. For 

 pollination see in text. 



Fig. 1775. — Erica cainea. Flowering 

 shoot in early spring. 



The fourth sub-family, Ericoideae, contains sixteen genera and 600 

 species, of which about 500 belong to the genus Erica. The majority are 

 confined to the Cape but several are found in this country, e.g., Erica 

 cinerea, Heather, and E. tetralix, Cross-leaved Heath. Calluna vulgaris, 

 Ling, is widespread in Europe and is interesting because of the endotrophic 

 mycorrhiza which it possesses. Many species of Erica (Fig. 1775) are 

 cultivated in gardens, and special Heather gardens are sometimes planted in 

 which, by a careful selection of species, flowers may be obtained all the 

 year round. 



In Erica tetralix the flowers are pendulous and pink in colour and are 

 pollinated by bees. The nectar is secreted at the base of the flower and a 

 proboscis 7 mm. long is necessary to reach it. The pollination mechanism 

 is essentially similar to that of the previous examples. Heather honey is 

 very important commercially, for the plants are in flower later than most 

 other nectar-producing species and the removal of hives to moorlands early 



