272 BRITISH PLANTS 
C. Woods on Calcareous Soils 
(e.g., chalk, limestone, maris, and other soils rich in lime). 
I. Ash-Oakwood Association.— On deep calcareous 
clay a wood intermediate between the damp oak-wood 
and the ash-wood is found in many parts. The oak and 
ash share dominance and the ground-vegetation is very 
similar to the damp oak-wood, but the wayfaring-tree, 
spindle-tree, and clematis are common here, yet rare in 
the oak-wood. The dogwood, privet, maple, sloe, and 
hawthorn also are far more abundant in this type of wood. 
Of the herbaceous undergrowth, the following are char- 
acteristic : Paris quadrifolia, Colchicum autumnale, Iris 
fetidissima, Epipactis media, EL. purpurata, and Cam- 
panula Tracheliwm. 
II. Ash-Woods.—These are the typical woods on lime- 
stone, where the soil is dry and poor in humus. The ash 
does not cast much shade, and the undergrowth is conse- 
quently rich and varied. The most frequent trees other 
than ash are the wych-elm (Ulmus montana) and haw- 
thorn. Many lime-loving species are present—e.g., white 
beam (Pyrus Aria), wayfaring-tree, yew, Inula Conyza, 
Scabiosa Columbaria, Carduus eriophorus (woolly-headed 
thistle), Origanum vulgare, etc. Heath-plants are absent, 
except where the limestone is covered with glacial clay 
or marl from which the lime has been washed out. 
This type of wood gradually merges into the ash- 
oakwood at low altitudes, as the soil becomes damper, 
and at high altitudes birches replace the ash. 
III. Beech-Woods.—The beech-wood is confined almost 
entirely to the chalk of South-East England, where it 
occurs as a zone on the borders of the damp oak-wood 
which covers the clay-with-flints on the top of the Downs. 
It also occurs to the west of England on the oolitic lime- 
stone of the Cotswold Hills. The branches of the beech 
are placed horizontally, and the leaves being situated in one 
plane, cast a very deep shade, which prevents the develop- 
ment of all undergrowth except a few mosses—e.g., Leuco- 
bryum. Every autumn the ground receives an enormous 
harvest of falling leaves, and as these decay slowly they 
form another unfavourable factor for the production of | 
ground-vegetation. The trees and shrubs present in the 
