WOODLANDS 269 



The scar-woods of the limestone-dales of the Pennines 

 are hazel-thickets, with ash as an occasional or frequent 

 associate. Mountain-ash, hawthorn, holly, sloe, buck- 

 thorn, dogwood, elder, wayfaring-tree, and privet also 

 occur, the first three being the most common. Plenty of 

 light penetrates to the soil, and the ground-vegetation is 

 rich and varied. Many plants of the limestone-cliff are 

 present (see p. 290), as well as shade-loving forms. The 

 latter include Sanicula europcea (wood-sanicle), Asperula 

 odorata (sweet woodruff), Lathrcea squamaria (toothwort), 

 Mercurialis perennis (dog's-mercury), Paris quadrifolia 

 (herb-paris), Scilla nutans (wild-hyacinth), and several 

 very rare plants — e.g., Polemonium cceruleum (Jacob's- 

 ladder), Cypripedium Calceolus (lady's-slipper orchid, now 

 almost extinct), Polygonatum officinale (Solomon's-seal), 

 and Convallaria majalis (lily-of-the-valley). 



The following classification of deciduous woods is that 

 adopted by Moss, Rankin, and Tansley.* 



A. The Alder-Willow Series. 



Dominant trees : Alnus glutinosa, Salix cinerea, and 

 S. Caprea. Found in very wet places, by marshes, streams, 

 and in fens (see p. 243). 



B. Woods on Non-Calcareous Soils, 



I. Oak-Woods — (a) Lowland Type. — The damp oak- 

 wood occurs on clays, loams, moist sands and gravels, 

 and clay-with-flints (covering large parts of the chalk- 

 downs of south-eastern England), up to about 600 feet. 

 It is most common in valleys and on alluvial plains rich in 

 humus. The trees are more luxuriant than on the up- 

 lands, and they cast a deeper shade. The herbaceous 

 ground- vegetation consists, therefore, either of shade-plants 

 or early flowering perennials, which bloom before the 

 trees are laden with foliage. Although the oak is domi- 

 nant, many other trees are present, and in some places 

 compete with the oak for dominance — e.g., ash, birch, 

 hornbeam. The ash is typically a tree of the limestone, 

 but it is common in damp lowlands as well, especially on 



* "The Woodlands of England," New Phytologist, vol. ix., 1910, 

 p. 113. 



