2€0 BRITISH PLANTS 
(see p. 89), and so we find the vegetation of limestone 
and chalk hills is made up of a mixture of these two types. 
The herbage on the windward side of the hill is short, the 
plants seldom rismg more than an inch or two above the 
ground, but in the sheltered parts the plants grow more 
luxuriantly, and it is here that most of the calciphilous 
plants mentioned below are found. 
The dominant grasses are Festuca ovina, Sesleria 
cerulea (in northern counties), Keleria cristata, and Pow 
pratensis ; common or frequent grasses are Agrostis 
vulgaris, Cynosurus cristatus (crested dog’s-tail), Brachy- 
podium pinnatum, and Briza media (quaking-grass). Aira 
flezuosa and Nardus stricta, so common on all other dry 
soils, are never found where lime is present—that is, they 
are typical calcifuges (see p. 89). The herbs found on 
the limestone-pasture and chalk-down include most of 
those occurring in the pasture on rich soil (p. 258). Other 
plants, associated with a dry soil, commonly found are = 
Potentilla Anserina (silver- weed), Veronica officinalis 
(common speedwell), Huphrasia officinalis, Carduus acaulis: 
(stemless thistle), and Daucus Carota (carrot). The calei- 
philous plants may be grouped according to their demand 
for lime as follows (those marked with an asterisk are 
more or less rare plants found only on chalk-downs in this 
country, although on the Continent, where they are more 
abundant, they may occur on other soils as well) : 
1. Confined to calcareous soil : 
Hippocrepis comosa (horse-shoe vetch), Aceras anthro- 
pophora (green man-orchid), and Polygala calcarea (chalk- 
milkwort, found only on the chalk-downs of South 
England). 
2. Almost exclusively found on calcareous soil : 
Anthyllis Vulneraria (lady’s-fingers), Ophrys muscifera 
(fly-orchid, growing usually at the top of downs under the 
shade of bushes), Campanula glomerata (clustered bell-. 
flower), and Buxus sempervirens (box-tree). 
3. Prefer calcareous soil : 
* Anemone Pulsatilla (pasque-flower), Helianthemum Cha-. 
mecistus (rock-rose), Polygala vulgaris (milkwort), Linum 
catharticum (purging flax), L. usitatissimum (common flax, 
linseed), L. perenne (perennial flax), Potertum Sanguisorba 
(lesser burnet), Viola hirta (hairy dog-violet), Asperula 
cynanchica (squinancy-wort), Centaurea Calcitrapa (star- 
