Park. In its way it crosses Combe Hill at 840 feet elevation, the highest point in the county.
From Combe Hill it goes toward the North East past Miswell to Tring; thence in a northerly direction to near Bulborne on Upper Icknield Way; thence nearly along the London and North- Western Railway to Seabrook, with the Ouzel district on the east; thence by Cheddington across the hill at Mentmore to Aston Abbots, and thence northwards to Stewkley North End; it then touches the Ouse district, and forms its northern boundary by Whitchurch, Oving, Quainton, Botolph Claydon, to Poundon.
The portion drained by the Ray is included in a line drawn from Poundon to Botolph Claydon, Quainton, Waddesdon station, and along the Wootton tramway to Muswell Hill, and thence by the Oxfordshire county boundary to Poundon.
The country contained within the Thame drainage is well diversified, the highest point in the county being within its area, while the Thame near Tythrop is only 230 feet above the sea. The prospect from Beacon Hill near Tring, and from Combe Hill near Wendover is of a very noble and beautiful kind, the reservoirs of Wilstone and Tring giving additional beauty, as water is usually lacking in midland scenery, while the views obtained from the top of Brill or Muswell Hills have a pleasing feature in allowing the observer to see all parts of a distant horizon and not merely a segment of a circle. The vegetation of the area is also a varied and interesting one. In addition to the plants mentioned as growing on the Chilterns in the Ouzel districtand the chief absentee is Carum Bulbocastanum we have recorded for the beautiful slopes of the chalk escarpment the musk orchis (Herminium Monorchis), the military orchid (Orchis militaris), a great rarity now limited to three or four of the chalk counties of the Upper Thames, the fly orchis (Ophrys muscifera), the winter green (Pyrola minor), the henbane (Hyoscyamus niger), the frog orchis (Habenaria viridis), the tower cress (Arabis hirsuta), the grass Bromus interruptus, the vetch Vida sylvatica, with its elegantly pencilled petals, the meadow sage (Salvia pratensis), the bedstraws Galium sylvestre (limited to this district) and G. erectum, the gentian (G. germanica), the chalk milkwort (Polygala calcarea), the eyebright (Euphrasia curta), the umbellifer Pimpinella major. The small flowered buttercup (Ranunculus parviflorui), occurs on gravelly ground near Bledlow, and in clayey soil the local sedge Carex axillaris occurs in one locality, the mint Mentha longifolia grows near Ellesborough and near Kimble the alkanet (Anchusa sempervirens) is naturalized. In the Dinton meadows the snake's-head (Fritillara meleagris) is plentiful, and white-flowered forms are not unfrequent. On the churchyard wall of Dinton Erinus alpinus is naturalized. At Stewkley South End there is a small marsh near a stream in which the bedstraw Galium uliginosum, and the dwarf valerian (Valeriana dioica) grow, and a field not far distant is the only known locality for the water avens (Geum rivale) in the north of the county, and only one is known for the south, namely that of the Chalvey meadows near Eton, and it is unknown for Northamptonshire although so frequent in many parts of Britain. In the Thame meadows near the town of that name the rush Juncm compressus grows sparingly. At Brill, 566 feet in altitude, the henbane (Hyoscyamus niger) is rather common, and the water buttercup (Ranunculus Drouetif) grows.
On the walls at Marsh Gibbon the stonecrop (Sedum dasyphyllum) is found; it is very frequent on the Coralline Oolite in Berkshire, where it may be native, but it is one of the rarest of the plants of Bucks. Sison segetum and Caucalis nodosa are found by the roadside near Ludgershall. At Boarstall, by the old moat, there is a considerable growth of the dock (Rumex maritimus), while near the decoy the cut-leaved form of the elder (Sambucus nigra var. laciniata), the jonquil (Narcissus biftorus) and the large daffodil (Narcissus major) are doubtless relics of cultivation.
The cultivated fields in the vicinity have the hawksbeard (Crepis biennis), as well as C. taraxacifolia, and the bushy hedgerows of the district contain fine examples of the roses Rosa glauca and R. systyla, as well as the hawthorn (Cratagus oxyacanthoides) and a probable hybrid of it with C. Oxyacantha.
There are not many introduced species in this district, but one of the ' duck farms ' near Brill has a plentiful growth of the cress Lepidium Draba, which when once introduced is difficult to eradicate, and on the London and North- Western Railway the white mignonette (Reseda alba) grew near Marsh Gibbon station.
4. The Thames District
This has its counterpart to some extent in the district ' No. 7. The Thames or Lower Thames' of my Flora of Oxfordshire, but it more closely resembles district 'No. 5. The
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