204 THE BOOK OF NATURE STUDY 



On the whole, the Molinia heath is more extensive than the 

 Nardus ; in some parts of the northern counties it may stretch 

 for miles on gently sloping, badly drained ground. These two 

 types of heaths represent respectively those developed under 

 extreme conditions of dryness and moisture ; as conditions 

 change, every possible gradation may occur. 



LIMESTONE HEATHS 



It is not always possible to draw a hard-and-fast line 

 between natural pasture and a heath. They may merge into 

 each other. In Somerset, heath plants, such as the Ling and 

 Bell-Heather, are found growing side by side with plants char- 

 acteristic of natural pasture, on carboniferous lime-stone. Where 

 the soil is shallow, pasture plants assert themselves ; where it 

 is more than three inches deep, heath plants are found. This 

 observation bears out the conclusion of the German botanist 

 Graebner, who in his work on the heaths of North Germany 

 states that typical heather formations can thrive in a soil largely 

 impregnated with lime salts. The soil of the limestone heath 

 is not peaty, but is of the nature of a red marl. Heather and 

 heath plants are found in Somerset on old ant-heaps, "emmets' 

 batches/' as they are called locally. The dominant plants on 

 those limestone heaths are : Furze, Hawthorn, dwarfed in growth, 

 Ling, Bell-Heather and a species of the grass Fescue. In York- 

 shire, some of the pastures are heathy in character, and are said 

 by the farmers to be " running back to moor." 



Grass heaths may occur at altitudes above 1000 feet. 

 When they occur at a height of two or more thousand feet 

 they are often characterised as Alpine Grass heaths. On such a 

 heath the Mat Grass is often replaced by the Heath Rush, and 

 Alpine plants may be found in sheltered crevices or by the side 

 of the mountain streamlets. The Blue Moor Grass (Sesleria 

 ccBYulea) is also commonly found in these situations. This grass 

 belongs especially to northern limestone hills; it has narrow, 

 flat, blue, stiff leaves, the stomata of which are sunk in and 

 guarded by six cells instead of two, thus preventing too great 

 transpiration. 



