TYPES OF SOIL

Sand

Characteristics : very pervious, dry and well drained, retaining little water by imbibition. Capillarity poor, well aerated; ’warm ’owing to low specific heat and low water content. Lacking in ’lime ’and potash and phosphates. Often acid and slightly peaty.

Vegetation : xerophytic sandy heath. Trees : conifers, birch, holly. Shrubs : gorsc, broom, whortleberry at high altitudes. Herbs: sheep ’s fescue, sheep ’s sorrel, heather, bracken. In damper sites : wavy-hair grass, sphagnum, drosera. Cultivated soil : many annual weeds, especially spurrey, poppy, corn marigold.

Clay

Characteristics : impervious, damp and poorly drained, retaining much water. Capillarity good, poorly aerated ; ’cold ’owing to high water content and specific heat. Lacking in lime and phosphate but containing much potash as a rule.

Vegetation : woodland and meadow. Trees : oak and elm. Shrubs: hawthorn. Herbs: primrose and wood anemone in shade ; wild carrot in hedgerows. Typical meadow flora : grasses, red clover, buttercups and thistles, etc. Cultivated soil : annual weeds not common—seeds do not easily germinate.

Chalk

Characteristics : well drained and aerated but with good 9A capillarity ; ’warm ’; generally well supplied in phosphates but lacking in potash ; on pasture upper layer poor in lime owing to leaching. Humus content low.

Vegetation—Trees : beech, yew, box, juniper. Shrubs : lacking, though hawthorn and sloe occur on the ’marls, ’ ; clematis in hedgerows. Herbs : thin pasture of sheep ’s fescue, rich in leguminous plants, e.g. bird ’s foot trefoil, small vetches, milkwort, burnet, scabious, viper ’s bugloss, marjoram. Cultivated soils : very weedy, typical weeds being fumitory and geranium molle.

Summary

The whole of the information given in the section on holophytic nutrition emphasizes the one important fact, namely, that green plants build up their own food from raw materials, thus differing in this respect from all other organisms except certain bacteria. The carbohydrates, lipides and proteins, which green plants do not make use of immediately, are stored for subsequent use. The parts which store such material become enlarged to accommodate it, and are therefore termed storage organs.

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