GRASSLAND ASSOCIATIONS 259 
small or narrow, so that the plants approach very closely 
to the rosette-plants in habit—e.g., Scabiosa Succisa 
(devil’s-bit scabious), Campanula rotundifolia (hairbell), 
and Pimpinella Saxifraga (small burnet-saxifrage). The 
most abundant creeping plants are: Trifolium repens 
(Dutch clover), 7. dubium (small yellow trefoil), Lotus 
corniculatus (bird’s-foot trefoil), Galiwm saxatile (heath- 
bedstraw), G. verum (lady’s-bedstraw), and Thymus 
Serpyllum (wild thyme). Where the soil is calcareous, 
lime-loving plants are common—e.g., Linum catharticum, 
Polygala vulgaris (milkwort), Viola hirta (hairy dog- 
violet), and Helianthemum Chamecistus (rock-rose). On 
dry soils heath-plants may be abundant—e.g., Ulex 
europeus (gorse, furze) and Pteris aquilina (bracken), 
together with scattered dwarfed plants of Vaccinium 
Myrtillus (whortleberry) and Calluna vulgaris (heather, 
ling). When these plants are abundant, the natural 
pasture passes over into a grass-heath. 
Alpine Pasture.—At an altitude of about 2,000 feet 
and over, a natural pasture may occur on rich soils. 
The dominant grasses are those found at lower levels, 
but Nardus stricta is more abundant, and may share 
dominance with the others, and the viviparous variety 
of Festuca ovina is common. But, above all, the alpine 
pasture is distinguished by the presence of alpine plants. 
of which Alchemilla alpina (alpine lady’s-mantle) is a 
constant and abundant representative. Most of the 
herbs occurring at lower levels are found here, and, in 
addition, the following alpines: Poa alpina, Potentilla 
Crantzii (alpestris, alpine cinquefoil), Cerastiwm alpinum 
(alpine mouse-ear chickweed), Lycopodium WSelago, L. 
alpina, L. clavatum (club-mosses), and—confined to Scot- 
land or North Britain — Sagina Linnei (mountain- 
spurrey), Ozytropis wuralensis, Gentiana nivalis, and 
Kobresia caricina. 
Limestone-Pasture and Chalk-Downs.—The soil formed 
on a hill composed of limestone or chalk is invariably 
dry, for the rock allows the water to drain away very 
rapidly—the chalk to a much greater extent than the 
limestone. The rock itself is very soluble in water con- 
taining carbonic acid gas, and the soil-water consequently 
contains a large percentage of bicarbonate of lime. 
Many plants prefer a dry soil, and others a chalky one 
