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Brenchley .— The Weeds of Arable Land . Ill . 
giving no effervescence when treated with dilute hydrochloric acid. These 
carstone soils are well seen at Dersingham, West Snettisham, and Heacham, 
and are usually of a decided red or yellow colour. The relative quantities 
of calcium carbonate in the sands are reflected in the flora, such so-called 
‘acid’ or 4 sour * plants as Rumex Acetosella and Spergula arvensis never 
being found on the calcareous sands. It is hardly correct to say that such 
plants as Rumex Acetosella are definitely symptomatic of c acid* soils. An 
acid soil is what is known to the agriculturist as a sour soil, the use of the 
technical word acid in this connexion being rather unfortunate. A sour soil 
implies one containing no chalk at all, so that an acid reaction is obtained 
with litmus paper. Rumex Acetosella will grow on soils which do contain 
a very small percentage of calcium carbonate, as can be seen at Blakeney 
Point, so that it is better to say that the so-called acid plants are really 
indicators of soils deficient in chalk, though total absence of calcium 
carbonate is not necessarily entailed. Warming 1 suggests that nearly all 
lime soils are rich in soluble mineral substances and that this wealth 
excludes plants belonging to poorer soils, owing to the competition of 
plants which flourish best on the richer soils. Cultures made by C. A. 
Weber and Grtibner have clearly demonstrated that none of the calciphobous 
plants, of which Rumex Acetosella is an example, suffer from lime when this 
is unaccompanied by a large amount of soluble salts, and that they are 
expelled from calcareous soils by competition. Nevertheless, from a practical 
agricultural point of view, the presence of calciphobous plants on any land is 
undoubtedly a sure indication of a deficiency of the chalk which is so 
essential to the well-being of most plants. 
In the present investigation sour soils other than sands have not often 
come into notice, so that it is not yet possible to say whether there is 
a flora that is characteristic of sour land of heavier texture. 
The lighter soils are characterized by the great diversity of plants 
composing their flora, a good proportion of the species being definitely 
characteristic of sand and sandy loams. The classification is as follows : 
Chrysanthemum segetum' 
Rumex Acetosella 
Scleranthus annuus 
Spergula arvensis 
symptomatic of light sandy soils 
which are very deficient 
in chalk. 
Bromus mollis 
Echium vulgare 
Erophila verna 
Lycopsis arvensis 
Myosotis collina 
- characteristic of sand . 
1 Warming, Eug. : Ecology of Plants, 1909, p. 67. 
