Page:VCH Berkshire 1.djvu/99

 BOTANY a great extent with the district ' 6. The Thame ' in my Oxfordshire Flora. It is of con- siderable size, and consists essentially of the vale of the White Horse. It also includes the north side of the chalk escarpment and the whole of the Boar's Hill range. It has for its boundaries on the west and north the Isis district just described, on the north-east the river Thames from Oxford to Mongewell, while the southern boundary passes from the Thames near Mongewell over King Standing Hill to East Ilsley, and then follows the Ridge road to the Wiltshire border on the south-west. The Ock is a stream with many head-waters, several of which spring from the junction of the chalk and gault ; in fact, the site of many villages at the base of the chalk escarp- ment were chosen on account of the presence of springs of clear pure water, and the bare chalk slopes were rejected, while the sheltered spots with water springs were selected by the early inhabitants, and villages grew up around them. These springs, which issue from the base of the hills at about 460 feet elevation above the sea, flow at first bright and sparkling, and are filled with ' cresses ' and the pondweed Potamogeton densum, but on reaching the clay of the vale are soon sullied. The vale part is to a considerable extent excavated in Kimeridge clay. The Wilts and Berks Canal traverses part of the district, and yields the local pondweed P. pnehngus as well as P. compressum (zostereefolius), P. Friesii and P. pusil- lum, and Tolypella glomerata also occurs. By its banks Cerefolium Anthriscus, Ceterach and Juncus obtusiflorus are found. One of the feeders of the Ock passes by Cherbury Camp, an interesting earthwork on which several local plants are found, and in the neighbourhood of which the pasque flower (Anemone Pulsatilla), the frog orchis (Habenaria viridis), the field chickweed (Cerastium arvense Orchis ustulata and Asperula cynanchica occur. Another, the Frilford brook, drains a particularly interesting piece of ground, in which are rich marshes and dry gravel commons. The latter afford the clovers Trifolium striatum, T. scabrum, T. arvense ; the cotton thistle (Onopordon Acanthium), which may be native here ; the bugloss (Echium), and the mullein (Ferbascum nigrum). Another and still more interesting feeder is a small brook with two or three branches which comes from Besilsleigh, and the branch which passes by Cothill forms a marsh which is one of the richest and most interesting in the midland counties. It is a very pretty bit of scenery, consisting of woodland merging gradually into marshland, with both bog and fen vegetation, so that there is the pondweed Potamogeton coloratus in its only known Berkshire locality, the bladderworts Utricularia major and U. minor, the sundew Drosera rotundifolia, the butterwort (Pinguicula vulgaris), the grass of Parnassus (Parnassia), the cotton grass (Eriopho- rum latifolium), the marsh orchids Epipactis pa/ustris, Orchis incarnata and 0. latifolia, the dropwort (OLnanthe Lachenalif), besides Samolus Valerandi, Echinodorus ranunculoides, Menyanthes, Anagallis tene/la, Valeriana dioica, Carex dioica, C. pulicaris, C. echinata, C. Bcenninghausiana, C. flava, C. Hornschuchiana, C. xanthocarpa, C. rostrata, Schaenus nigricans, Molinia, Juncus obtusiflorus and Cnicus pratensis. In the drier portions Genista tinctoria, G. anglica, Lithospermum officina/e and Euonymus occur. In its lower course this brook has marshy ground on its margin, where the peppermint (Mentha piperita) and the spearmint (M. longifolia var. villosa, Sole) occur, the latter in great quantity. The high ground of the Boar's Hill range, with Cumnor Hurst and the coppices about it, and Bagley Wood is also very productive ground to the botanist, although building opera- tions threaten to destroy some of the county which is most prolific in rare plants. The northern side is marked by watercourses which have cut their way through the soft strata, and in one of these, now occupied by the ' rifle butts,' there is a large quantity of that elegant plant Scirpus sylvaticus. The village walls of Hinksey give Sedum dasyphyllum, which appears to be native in this district, so widely distributed is it, the navelwort (Cotyledon Umbilicus), the shining cranesbill (Geranium lucidum), and the round-leaved cranesbill (G. rotundi folium), the last a very abundant plant on the coralline oolite, but which rapidly thins out or disappears on the more southern strata. The summit of Boar's Hill from whence may be seen one of the most beautiful views in the county, comprising as it does the vale of the White Horse, the coast-like range of the chalk hills, the woodland tracts of Bagley and Wytham, and the spires and towers of Oxford immediately below is especially characterized by the rich bramble flora which it affords. Here, in one of the few spots known in Britain, is Rubus Colemanni. Another very handsome species is R. sulcatus, and R. flssus, R. mercicus var. bracteatus, R. nessensis, R. holerythros, R, idaus var. anomalus, R. affinis, R, Marshalli, R. Sprengelii, R. putescens, R. oigoclados, R. folio- sus, R.fuscus, R. rudis, and many others have been found. The marsh violet (Viola pa/ustris) occurs where it was first mentioned by Dr. Plot, the beautiful horsetail (Equisetum syhaticum), 53