WOODLAND PLANTS 349 



also, that while some species are restricted in their distri- 

 bution, others (e.g. Bracken) are much more plastic, and 

 persist in very varied habitats. 



In the typical moist Oak woods on siliceous soils the 

 above-mentioned species, along with many others, occur, 

 and the ground flora is often a bright flowery carpet. 



Ash woods on calcareous soils. In woods on calcareous 

 soils the ground flora is still more varied. Oaks are rare, 

 the Common Ash tends to occupy the first place, accom- 

 panied by shrubs like the Hazel, Wayfaring Tree, Spindle 

 Tree, White Beam, Buckthorn, Dogwood, and Privet. 

 Among the herbaceous plants the Dog's Mercury is a very 

 abundant social species covering large areas. Others com- 

 mon or frequent are Primrose, Cowslip, Wood Crane's-bill, 

 Blood Crane's-bill, Avens, Strawberry, Great Burnet, Stone 

 Bramble, Spurge Laurel, Hellebore, Small Scabious, Lily- 

 of-the-Valley, Solomon's Seal, several Orchids (e.g. Tway 

 Blade, Helleborines, and Purple Orchis), False Brome- 

 grass, and Brittle Bladder Fern. The Bracken is usually 

 inconspicuous and often absent. Thus Oak woods on 

 siliceous soils and Ash woods on calcareous soils form two 

 well-recognized types of woodland. 



As we have seen, woodland species extend along the 

 hedgerows, and reference should be made to the groups of 

 plants mentioned in Chapter XXVII for further examples, 

 especially of climbing and scrambling plants, whose natural 

 habitat is the woodland. 



If we take a general view of the plants in a wood we see 

 at once that they tend to occupy successive layers. The 

 highest is the tree layer, below which is a layer of shrubs, 

 and lower still are layers of tall, intermediate, and low- 

 growing herbaceous plants (Fig. 224). 



With such a succession of overshadowing layers it is 

 obvious there must be considerable accommodation among 

 the different species. To watch these layers throughout 



