Iv] GRASSLAND ASSOCIATIONS 105 
in the same plant formation. On the Pennines further north 
(see Smith and Rankin, 1903: 154), similar sub-Alpine pasture 
occurs; but there one species, Poa alpina, occurs which has 
not been found in the Peak District. Sub-Alpine pasture, 
characteristic of the Scottish mountains, has been described 
by R. Smith (1900 b: 454). 
On the calcareous soils, the grassland is poor in heath-loving 
or humus-loving species but rich in lime-loving species, and this 
association is termed calcareous grassland. A certain number 
of species (see the lists of plants given later on in the chapter) 
are common to siliceous grassland and calcareous grassland. 
The two types of grassland are related, directly or indirectly, to 
the presence or absence of calcium carbonate in the soil. On 
the limestones, it is only at the higher altitudes, where the soils 
are leached by rain and therefore contain much less lime, that 
calcareous grassland approaches siliceous grassland in its eco- 
logical and floristic characteristics. On the lower slopes of the 
caleareous hills where the soil is rich in lime, the acidic 
humus which favours the growth of the plants of the siliceous 
grassland does not appear to be formed; and it certainly does 
not accumulate. 
A certain amount of grazing of sheep and cattle takes 
place on many parts of the grassland; but the amount is, on 
the whole, rather small. The land is not artificially manured 
or drained. On the sub-Alpine grassland, no grazing or 
manuring takes place at all. 
Other types of grassland occur in other parts of the country, 
more especially in central and southern England. Clayey and 
fresh loamy soils, for example, are characterized by the absence 
of both humus-loving and of lime-loving species; and the 
grassland of such soils may therefore be termed neutral grass- 
land. A fourth type occurs on the flat lands which occur near 
rivers and which are liable to periodical inundations: this may 
be termed alluvial or fen grassland. An analysis of the 
grasslands of Orkney has recently been published (Scarth, 
1911). 
“Permanent pasture” is an agricultural term in use in 
this country to denote grazing land which has, in general, 
been ploughed up at least once, and which is artificially 
manured (see Chapter VIII). 
