XXIV FLORA OF OXFORDSHIRE. 
northwards to include Fritwell, sweeping round to include Hor- 
well Farm, and joining the turnpike road to Brackley, which then 
forms the border to the Northants boundary, marching with that 
county to the Bucks border, the river Ouse itself limiting it to 
the north-east. Its eastern boundary is Buckinghamshire by 
Goddington to Poodle Farm. Its southern border is along the 
road from Poundon to Fringford, the latter place being included 
in it, then strikes off westwards so as to take in Hethe Braid, 
Stoke Lyne, Swift's House, to Ardley, where the Castle is 
probably the top of the watershed, and continues from Ardley 
towards Somerton, just omitting Chilgrove and Somerton field 
barn. The drainage is principally by a small stream rising a 
little east of Somerton, flowing by Fewcott, Stoke Lyne, and 
Hethe Braid, to Fringford, and thence by Goddington into 
Bucks. The main stream of the Ouse forms the county boundary 
for 4 or 5 miles, draining the parishes of Mixbury and Finmere. 
Geologically it is almost entirely on the Great Oolite, the surface, 
however, being much obscured by drift deposits. Near Fringford 
there is a small area on the Cornbrash. The most interesting 
portions are Cottisford Heath, Tusmore and Hardwick Heath 
(Oolite overlaid with flint gravel) which yield Gentcana Ama- 
rella, Orchis pyramidalis, Carlina vulgaris, Campanula glome- 
rata, Leucojum vernum (extinct), Helianthemum vulgare, Stellaria 
graminea, Hypericum pulchrum, Rubus rhamnifolius, R. leuco- 
stachys, R. rudis, R. Koehleri, R. diversifolius, Rosa tomentella, 
kt. pruinosa, R. latebrosa, Parnassia palustris, Galium verum, 
Carduus acaulis, C. lanceolato-crispus, C. nutant-crispus, 
Linaria spuria, Calamintha Acinos, Typha latifolia, Potamo- 
geton densus, Carex binervis, Gymnadenia conopsea, Brachypo- 
dium pinnatum, Triticum caninum, Polystichum aculeatum, 
Hypericum humifusum. Ardley wood yields Daphne Mezereum 
(adv), Helleborus viridis, Aquilegia vulgaris, Campanula Trache- 
hum, Hyrthrea centaurium, Luonymus, Berberis, Hordeum syl- 
vaticum. 
Other interesting plants of the district are Thalictrum 
riparium, Trifolium medium, Ribes nigrum, Geranium pyrenat- 
cum, Tanacetum, Malva moschata, Valeriana dioica, Alchemilla 
vulgaris, Lithospermum officinale, Hippuris, Nepeta Cataria, 
Lysimachia nemorum, Astragalus glycyphyllus, Spirea Filipen- 
