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 A HISTORY OF BERKSHIRE The Bagshot Beds form the high grounds of Cold Ash Common, Hartshill and Bucklebury Commons. South of the Kennet they extend from Inkpen Common to Greenham and Crookham Commons, and the commons of Brimpton, Tadley, Silchester and Burghfield. Here a gap occurs owing to the denudation of these beds from the valley of the Loddon ; they reappear however near Risely Common, and the main mass rises up to form the beautiful Finchampstead Ridges, and covers a considerable tract of the country which extends from Wokingham and Sandhurst to Ascot racecourse, Sunninghill and the border of Virginia Water. The elevated ground of Cassar's Camp, Wickham Bushes, Easthampstead Plain, Tower Hill, etc., belong to the upper Bagshot sands, and are often covered with pebble drift. In the Windsor district the lower Bagshot Beds are to be seen about Cranbourn Lodge, and in the wood near the stream has cut itself through to the London Clay. A very interesting flora is to be found on the great tracts of heath- lands, pine woods, numerous and rather extensive bogs and open com- mons which is formed of the Bagshot Beds, but it is much too large to be quoted in full ; moreover, as has already been hinted, the occurrence of certain plants appears to be induced by the condition of porosity or imperviousness, by the presence or absence of peat or humus, by sun and wind exposure, by shade from sun or shelter from wind, and such physical causes, rather than by the various geological strata on which they grow, except inasmuch as these in themselves act as any of the above factors in plant distribution. The contrast between the country formed by these Bagshot Beds is however very marked from that of the more northern parts of the county. Instead of the rich meadows of the Oxford Clay and its oak woods, studded with primroses or blue with wild hyacinths, or the stone walls and houses of the Corallian Beds, or the flat uninteresting agrestal districts of the Kimeridge and Gault, or the gently undulating and fertile greensand, with its fields of blazing poppies and crimson clover (Trifolium incarnatum), or the crisp turf of the chalk downs, redolent of thyme, with its maple and buckthorn hedges and its fields sometimes dazzlingly yellow with mustard, at other times white with corn camo- mile instead of these we have an area to a great extent uncultivated, sometimes showing a golden coloured common owing to the abundance of the dwarf gorse (U/ex minor), or crimson with the heath (Erica cinerea), or amethystine with the heather (Calluna Erica). In other parts great tracts of sombre pine woods, showing on their borders the grass Agrostis setacea, an Atlantic species here perhaps in its most easterly situation ; or it may be we observe a shallow trough or valley, with somewhat sombre colouring, caused by the combination of the cross-leaved heath (Erica Tetralix) and the grass Molinia varia, among which grow the sweet gale (Myrica Gtf&),with here and there the sedge Carex echinata, the orchid O. ericetorum, the rich orange spikes of the Lancashire asphodel (Narthecium ossifragum), and the meadow thistle (Cnicus pratensis). In drier and more exposed situations we may observe 48