266 МК. В. 8. ADAMSON : AN ECOLOGICAL STUDY 
It can be divided into two sub-societies 
a dry and а damp one. 
One feature separating both these from the other societies of the calcareous 
clay is the depth to which roots extend; in the others even shrub-roots do 
not penetrate more than about 7 inches, while here the roots of hazel extend 
to well over a foot. 
Mercurialis perennis Society. (1) Dry TYPE. 
This is confined to small areas in the wood, all at or near the edges, along 
banks beside the boundary diteh especially. In addition, there are isolated 
patches on mounds in other societies. The maximum water-content here is 
38'5 per cent. and the mean annual amount 31:16 per cent., while in the 
summer it falls to 22-24 per cent. In dry weather in summer the soil may 
become very hard and crack freely at the surface, when very little water is 
present in the first 1} ins., though below the soil is comparatively wet. This 
condition does not occur in other societies except in open parts, and is 
correlated with the greater evaporation rate on the ground. 
Mercurialis perennis is dominant and is often very nearly pure; prominent 
mong the associates are : 
Fragaria сезей....... sss а 
Viola Riviniana а sss о 
Seilla nonseripta уд... la 
(теит urbanum о. о 
with some others rather less abundant :— 
Cares sylvatica а о 
Anthoxanthum odoratun............... О 
Lamium Galeobdolon а. lo 
Arum maculatum — ...... .. "EN e 0 
Tamus communis....... ааа. S00 
Heracleum Sphondylium............... r 
Hypericum hirsutum 000000. la 
In this Society Scilla nonseripta may be very abundant, even showing 
dominance locally. Scilla and Mercurialis form а good example of an 
edaphically “ complementary ” society *. 
, 
С 
Mercurialis perennis Society. (2) Damp ТҮРЕ. 
The above society passes directly into the dump Mereurialis perennis Society, 
which has a rather higher percentage of soil-moisture, the summer average 
being 25-26 per cent. There is no sharp line between these two. In this 
* Woodhead, 1906, p. 345. 
