355 MR. К. S. ADAMSON: АХ ECOLOGICAL STUDY 
August. The minimum occurs in May—30 per cent. This soil dries very 
evenly to considerable depths; but, owing to its high water-holding capacity, 
never gets very dry. 
In general, the soil of the Sp/rea-Deschampsia Society has very much the 
хате water-content as the Spirwa Society ; it is usually slightly lower, but 
has a higher minimum—-32 per cent.--and is more ару variable in summer, 
Another factor that seems to influence the variations in soil-moisture 
between the last two societies, as compared with the Mercurialis Society, is 
that in them there is often a layer of mosses on the surface, which is practically 
absent from the latter. 
Details of the Plant Societies. 
CALCAREOUS CLAY. 
I. Spirea Ulmaria Society. 
II. рга Ulmaria and Deschampsia cwspitosa Society. 
III. Mercurialis perennis Society. 
IV. Fragaria vesca Society. 
Loam, 
— 
Pteris aquilina and Holcus mollis Society. 
Holcus mollis Society. 
— 
— 
. 
PLANT SOCIETIES OF THE CALCAREOUS CLAY. 
Г. Spiræa Ulmaria Society. 
This society falls into two divisions, depending mainly on the amount of 
light. | 
Spirea Ulmaria Society. (а) Suave Form, 
Where the shrubs are nearing the end of their rotation the ground flora 
is much less dense than where more light penetrates. In such situations the 
ground flora is usually dominated by Spirea Ulmaria, associated with several 
other plants, such as :— 
Primula elatior ............ a* | Carex sylvatica ............ о 
P. vulgaris „ан... la | Nepeta hederacea ......... la 
Anemone nemorosa......... o-a | Angelica sylvestris ,........ o 
Scilla попке р. lo 
* The following signs are used to indicate the relative abundance :—d, dominant; 
3, subdominant; a, abundant ; o, Occasional; r, rare; vr, very rare; 1, local; 
la, locally abundant ; lo, local, but: occasional, 
