ANGIOSPERM^, DICOTYLEDONES. 



769 



The pollen is dusty in Ericaceae, but adhesive in most other cases. The pollen-cells 

 are united in fours in Ericaceae, Rhodoracese, and Pyrolaceee, and in the Rhodoracese 

 these groups are connected by tough threads (see figs. 219 ^' 2> *> p. 101). The fruit 

 is capsular in Diapensiaceae, Pyrolaceae, Monotropaceae, Rhodoraceee, Ericaceae, and 

 Epacridaceae, and baccate in Arbutacese, Empetraceae, Sapotaceae, and Ebenaceae. 

 In the Lennoaceae the fruit resolves itself into 10-28 one-seeded portions. The 

 Ericales are distributed over the whole world; the Ebenaceae and Sapotacese live 

 chiefly in the tropics; the Lennoaceae are confined to the southern half of North 

 America, and the Epacridaceae to Australia. The species of Ericacege are most 

 abundant at the Cape. Most of the species of the genus Rhododendron inhabit 



Fig. 433. — Ericales: Arbutus Unedo of the family Arbutace». 



1 Flowering branch. 2 Three flowers magnified, s Longitudinal section through a flower. 

 has been removed, s papiHose berry. 2, 3 and * maguifled, (After Baillou.) 



* Flower from which the corolla 



the mountains of Central Asia, e.g. the Himalayas. The genus Kcdmia belongs to 

 the mountains of North America. The Diapensiaceae live in the arctic regions, as 

 also do several Ericaceae. Loiseleuria or Azalea procunibens is widely distributed in 

 the arctic regions, and also occurs in exactly the same form on the mountains of 

 Central and Southern Europe ; in the Central Alps it attains its maximum elevation 

 of 2700 metres above the sea-level. Most of the Ericales grow sociably on rocky 

 declivities in mountainous districts, and on sandy soil in plains. Many only 

 flourish on moorland, or when rooted in a deep layer of humiis, and these play an 

 important part in the formation of peat. Fossil remains are found in the deposits 

 of the Mesozoic, Tertiary, and Diluvial periods. The number of extant species 

 known is about 2300. 



Vol. il 



99 



