having its headquarters in the county is the calamint (Calamintha parvifolia or Nepeta), which is locally very abundant on the dry banks in the neighbourhood of West Wycombe, Chalfont St. Peter's, Seer Green, etc. The maple and holly are plentiful in the hedgerows, and the buckthorn (Rhamnus catbarticus), the wayfaring tree (Viburnum Lanfana), the true cherry (Prunus Cerasus), as well as P. avium, occur.
The Reading Beds are the lowest members of the Tertiary strata found in Buckinghamshire: they consist very largely of stiff clay mottled with a great variety of colours, but they also include beds of sharp sand, also variously coloured, and loams. They rest unconformably on the Chalk, and once formed an unbroken sheet over its whole area, but they have been largely removed by denudation; the various outhers such as those at Penn however testify to the much wider range they formerly had. The Reading Beds now occupy a considerable surface of southern Bucks about Wooburn, Burnham, Beaconsfield, Hedgerley, Chalfont St. Peter's and Denham.
The varied soils formed by these beds necessarily give rise to a diversified flora, and it is rendered even more interesting from the extensive deposits of drift gravels by which in many places they are covered. Therefore in quick succession we find purely ericetal species such as the trailing St. John's wort (Hypericum humifusum) and bird's-foot (Ornithopus perpusillus), and clay-loving species such as Mentha rubra and M. piperita.
Where the drift gravels are common we then find a most interesting series, such as the silvery cinquefoil (Potentilla argentea), the subterranean clover (Trifolium subterraneum), the soft clover (T. striatum) and the hare's-foot (T. arvense), the buck's-horn plantain (Plantago Coronopus), the tower-cress (Arabis perfoliata), the climbing bindweed (Polygonum dumetorurn) the cress (Lepidium heterophyllum var. canescens), the hawkweeds H. boreale, H. sciaphilum and H. umbellatum, the saw-wort (Serratula tinctoria), the Deptford pink (Diantbus Armeria), the broomrape (Orobancbe Rapum-genlstae), the pearl-wort (Sagina ciliata) and very locally S. subulata. The less pervious clays have afforded the sedges Carex strigosa, C. elata, and chamomile (Anthemisnobilis) .
The London Clay is another Eocene formation, and it is found resting on the Reading Beds as a stiff brownish clay, often containing large nodules of calcareous matter called septaria, but is usually very uniform in its character throughout its whole thickness, which is not less than 300 feet in some places. It occupies a large tract of country between Slough, Langley and Drayton, where it is extensively excavated for brickmaking, and Stoke Common, Fulmer, Red Hill are also situated on it, while there are extensive outhers capping the Chalk, as at Lane End, which is 593 feet in altitude, and the neighbouring eminence of Priests is 606 feet above sea level.
Like the Reading Beds, this formation is often covered with drift gravels, and then we see in close proximity the ericetal and glareal
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