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 rotundifoUa (hairbell), 

 and Pimpinella Saaiifraga (small bur net-saxifrage). The 

 most abundant creeping plants are : Trifolium repens 

 (Dutch clover)j T. dv^ium (small yellow trefoil), Lotus 

 corniculatus (bird's-foot trefoil), Galium saxatile (heath- 

 bedstraw), Gf. verum (lady's-bedstraw), and Thymus 

 Serpyllum (wUd thyme). Where the soil is calcareous, 

 lime-loving plants are common — e.g., lAnum catharticum, 

 Polygala vulgaris (milkwort), Viola hirta (hairy dog- 

 violet), and Hdianfhemum Gharnicecistus (rock-rose). On 

 dry soils heath-plants may be abundant — e.g., Ulex 

 europcBU^ (gorse, furze) and Pteris aquilina (bracken), 

 together with scattered dwarfed plants of Vaccinium 

 Myrtillus (whortleberry) and Galluna 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 pastm-e 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 

 Grantzii [alpestris, alpine cinquefoil), Cerastium alpinum 

 (alpine mouse-ear chickweed), Lycopodium Selago, L. 

 alpina, L. clavatum (club-mosses), and — confined to Scot- 

 land or North Britain — Sagina Linnoei (mountain- 

 spurrey), Oxytropis uralensis, Gentiana nivalis, and 

 Kohresia caricina. 



Limestone-Pasture and Chalk-Downs. — The soil formed 

 on a hill comjyosed 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 



