MOORLAND PLANTS 227 



example. Of the genus Vaccinium two species, the 

 Cranberry and the "Cowberry, are evergreen, but the 

 Bilberry l and V. uliginosum are not ; Arbutus is ever- 

 green ; one species of Bearberry has evergreen, the 

 other deciduous leaves ; Andromeda, Erica (five 

 species), Calluna (Ling), Dabeocia, Phyllodoce, 

 Loiseleuria and the five species of Pyrola are all 

 evergreen. 2 



As to the Bilberry, which is one of the few deciduous 

 Ericaceae, it is to be remarked that it is not a charac- 

 teristic moorland plant, but overspreads the grassy 

 borders of the moors, where it chiefly competes with 

 Ling and the grass Nardus. In spring and early 

 summer the quick growth of the Bilberry shoots 

 enables them to overtop its rivals, and thus to get an 

 advantage which lasts all through the season. When 

 winter approaches, the Bilberry gives up the struggle, 

 casts its leaves, and appears to die down. It does 

 not really do so, however. The younger stems remain 

 green, and as they are provided with numerous 

 stomates, they no doubt assimilate during the short 

 hours of winter sunshine. In summer the deciduous 

 leaves of Bilberry can safely expand far more freely 



1 The leaves of Bilberry often remain green through the 

 winter in sheltered places, but elsewhere they are usually 

 deciduous. 



2 The word evergreen does not always bear precisely the same 

 meaning. It is applied to leaves which are able to endure 

 frost, and last through a great part or the whole of winter, 

 being all renewed at once in spring. Most of the Ericaceae 

 are only evergreen in this sense. In other cases the leaves are 

 changed a few at a time, usually in summer. The tree is never 

 bare, and the leaves may last more than one year. 



Q 2 



