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Rh (Prunus spinosa) in the hedgerows. The flora of the road borders on the clay will be found to consist principally of the grasses Dactylis glomerata, Poa trivialis, P. pratensis, Lolium perenne and Festuca pratensis, and occasionally F. arundinacea, and the great plantain (Plantago major) and the strawberry-headed clover (Trifolium fragiferum) are common. In the ditches there will be the teasel (Dipsacus sylvestris), the ragwort (Senecio erucifolius), the fleabane (Pulicaria dysenterica) and the mint (Mentba aquatica), and the thistles will be usually Cnicus lanceolatus and C. palustris, whereas on the oolite the grasses more commonly found will be Poa pratensis, often as the var. subcaerulea, Bromus erectus, Avena pubescens, Cynosurus cristatus, Festuca ovina and F. rubra, and the plantain will be more frequently Plantago media. The pastures will offer abundance of cow-slips (Primula veris), and when there is a rich subsoil there will often be immense quantities of the green-veined orchid (Orchis morio). If there be little subsoil we shall see abundance of the thyme (Thymus Chamcedrys), or the rock-rose (Heliantbemum Chamcecistus), The thistles will be Carduus nutans or even possibly Cnicus eriopborus and frequently C. acaulis. Even the cornfield weeds are different, for on the calcareous soil we shall find the shepherd's weather-glass (Specularia bybrida), Linaria Elatina and L. spuria, the corn gromwell (Litbospermum arvense) and occasionally the rarer form of the pale poppy (Papaver Lecoqii).

But as I have said, this band of oolite stretching across the northern part of the county is not a continuous zone. For considerable distances it is covered with drift deposits, and when these consist of gravels we shall have plants fond of warm and porous soils, while if the surface deposit consist of Boulder Clay we shall have the same pelophilous species which abound on the Oxford or Kimeridge Clays. An example may be worth quoting : When I began systematically to work the county about six years ago I found there was no certain record of the woolly-headed thistle (Cnicus eriophorus) for the county. Now I well remembered as a boy seeing it in a portion of Whittlebury Forest, the haunt of the chequered skipper, in Northamptonshire, and just at its south-western extremity, where there is a turnpike road leading from Whittlebury to Wicken. This road is within a few yards of the county border, so that one might almost have been justified in assuming that in this place the thistle would spread into Bucks. But in order to see if this were the case I went over and found this handsome thistle growing with the rock rose in the spot I remembered, and also extending along the eastern side of the road, but I also saw what the map did not tell me, that there was a sudden change in the soil on the south-western side of the road, for while on the Northamptonshire side the oolite was at the surface, on the Buckinghamshire side a drift deposit obscured the limestone, and not a single specimen of the thistle or rock rose could I see within the Buckinghamshire boundary, although I made a close search, nor did I see it in my walk of seven or eight miles towards Buckingham, but shortly before reaching Westbury I had the pleasure of gathering it in a spot where the oolite once again appeared. I have since found it in great