The fauna and flora of Hertfordshire, like those of other counties with varying geological formations, are not, however, by any means the same everywhere. On the contrary, there are well-marked local differences mainly associated with what naturalists call “station”; that is to say, differences of elevation, soil, geological formation, climate, etc., etc. The animals and plants of the high chalk downs in the neighbourhood of Gaddesden, Dunstable, and Ashwell, are for instance more or less markedly distinct from those of the lower level corn-growing areas of the centre of the county. On these elevated tracts we find, for example, wheatears, stone-curlews (near Tring), blue butterflies, burnet-moths, small brown-banded white snails, a periwinkle-like snail with a horny door to its shell known as Cyclostoma, blue gentians, certain orchids, and many other kinds of plants rarely or never seen on the low grounds. The open commons and heaths, on the other hand, as has been already mentioned, are the home of heather and gorse, together with various distinctive birds and reptiles, such as stonechats, whinchats, titlarks, goldfinches, vipers, slow-worms, and lizards. In the river-bottoms and other swampy localities we find marsh and water-birds, such as yellow wagtails, snipes, sandpipers, grebes (at Tring), herons, moorhens, water-rails, coots, dabchicks, and wild duck, together with (locally) the common grass or water snake, amber-snails, marsh-marigolds, purple loose-strife, ragged robin, reeds, and yellow flags. Beech trees, as mentioned above, form the predominant timber on the chalk-lands other than the high downs, while on the heavier soils of the centre of the county their place is mainly taken by elm and ash. On these lowlands and other open cultivated tracts are found such birds as partridges, corncrakes, lapwings, pipits, and larks; while in the coppices, hedgerows, and gardens we look for nightingales (from which bird Harpenden takes its name, _haerpen_ being a nightingale and _dene_ a valley in Anglo-Saxon), blackcaps, whitethroats, wrens, and nuthatches; while the woods are the resort of green and spotted woodpeckers, wood-pigeons, jays, and pheasants. The low grass-growing clay-plains on the southern side of the county support, as already stated, an abundant growth of oaks to the almost complete exclusion of other timber trees; and this area doubtless also presents certain peculiarities in its fauna distinguishing it from the corn-growing tract to the north. The oaks grow to a very great size, especially at Sacombe and Woodhall Park, and three notable specimens in the county are Queen Elizabeth’s oak at Hatfield, Goff’s oak at Cheshunt, and the Panshanger oak. In addition to these local peculiarities in the fauna dependent upon elevation, geological formation, soil, and the presence or absence of forest, there are, however, certain others for which climate may possibly account.