THE DICOTYLEDONES 1859 



In this connection we shall follow Engler as regards both the families 

 included in the order and also in the limits which he sets for the Ericaceae. 

 Of the families which he includes we shall mention only three, Pyrolaceae, 

 Epacridaceae and Ericaceae. Before considering the Ericaceae in detail we 

 may briefly refer to the other two families. 



The Pyrolaceae include some thirty species grouped in ten genera. 

 They are confined to the Arctic and cold north temperate regions. Two 

 genera occur in Britain, Pyrola (Fig. 1761) and Monotropa (Fig. 1762). 

 The former is an evergreen plant with a creeping rootstock. The latter is a 

 colourless saprophyte occurring rarely in Birch and Beech woods. Below 

 ground it has a much-branched root system, covered by an ectotrophic mycor- 

 rhiza, while the flowering shoots originate from adventitious buds. 

 Similar modifications occur in Moneses uniflora in which there is no 

 stem, the solitary flower arising from a bud on the roots. These and other 

 examples of the family show remarkable specialization and reduction in 

 floral structure, and it is interesting to note that among other features of 

 reduction no cotyledons are produced by the embryo. 



The Epacridaceae are a larger family containing about 3:50 species, 

 distributed chiefly in Australia and Tasmania, but extending eastwards to 

 South America and westwards to India. They strongly resemble the 

 Ericaceae in habit. It is interesting to find that while their centre of 

 distribution is clearly Australia, that of the Ericaceae is mainly in Africa 

 [Erica) and western China [Rhododendron). They may thus be said to be the 

 Australian counterpart of the Ericaceae. Several are cultivated in this 

 country as greenhouse shrubs. 



Ericaceae 



The Ericaceae are a widely distributed family of woody shrubs with 

 alternate, opposite or verticillate leaves, which form an important facet of 

 the flora of moorlands. Many are alpine plants and most of them are ever- 

 greens. The family is represented in Britain, firstly by the Heather and 

 Ling which abound on almost every common or moorland. To a somewhat 

 less extent it is also represented by the Cranberry and the Whortleberry or 

 Bilberry which, though not as widespread as the former plants, cover wide 

 stretches of country, particularly in western and northern districts. In the 

 second place the family is represented by introduced plants, particularly 

 the Rhododendrons and Azaleas, one of which, R. ponticiim, has multiplied 

 naturally in many parts of the western counties and in the Scottish high- 

 lands to such an extent that it forms the dominant shrub of the pine woods. 



A number of species of Heather occur in this country. Erica cinerea 

 (Bell Heather), E. tetralix (Cross-leaved Heath), and Calluna vulgaris 

 (Ling) being the most important. Vacciniiim myrtillus (Fig. 1763) is the 

 Whortleberry or Bilberry, while other related species are V. vitis-idaea 

 (Cowberry), V.oxy coccus [Cxznhtrry) and V . uliginosuni[^og\N\\orX.\thtrry). 

 In the highlands of Scotland two species of Arctostaphylos occur: A. uva- 



