sulphate and carbonate of lime to allow plants such as the sundew or the Lancashire asphodel to grow. There are interminable series of pastures wearisome in their monotony, but in some of the meadows near Ayles- bury the snake's-head (Fritillaria meleagris) is as common as it is in the better-known locality of Oxford, and here from its being in such a sequestered and unpopulated region, the indigenity of this interesting species in the Upper Thames province is further strengthened. The clay, which is often bituminous, with irregular bands of limestone nodules, is sometimes of a dull leaden colour, as near Hartwell and Aylesbury, where it is extensively worked for brick-making. Here and there are tracts of woodland in which the oak is the prevailing tree, although both species of elms attain large dimensions ; and the black poplar, always slightly leaning to one side, and not I think always against the wind, is a conspicuous feature in the low fields of the Vale, while the course of the small, sluggish and turbid streams is marked by the line of pollard willows, while the hop (Humulus Lupulus) and the large bindweed (Calystegia septum) and the water stitch wort (Stellaria aquatica) the willow herbs Epilobium hirsutum and E. parviflorum, and the loose- strife (Lythrum Salicaria) break by their display of colour the somewhat dead monotony of the scene.
The Portland Beds are more largely represented in Buckingham- shire than in Oxfordshire ; the main outcrop passes north-east from Thame, forming a tract of drier soil, by Cuddington and Dinton to Bierton and Aylesbury, where the rock is soft and sandy ; and there are outlying masses at Brill, Muswell Hill, Ashendon, Whitchurch, etc. Capping the Portland Beds are the Purbeck Beds at Brill, which exist as thin beds of drab-coloured close-grained limestones of fresh- water origin, but they have not the characteristic calcareous flora to the same degree as the Great Oolite or the Chalk.
The Lower Greensand, which is formed of the lowest beds of the Cretaceous formation, are of very irregular occurrence, but they may be traced at intervals across the counties of Berks, Oxford and Bucks, rising above the flatter and less elevated clay tracts by which they are surrounded. We find that in the two first-named counties the well- known hills of Faringdon, Boar's Hill and Shotover, consisting essen- tially of the Greensand, are not only very striking and pleasing factors in the effect they produce upon the outline of the country, but from their being of a warm porous rock, overlying an impervious stratum, the juncture of which is marked by a line of springs which offer a congenial home for many interesting marsh plants, and from the water often containing ferrugineous matter in solution, a true bog is formed ; so that on this formation we obtain a more diversified flora than on any of the previous formations yet considered. Nor does the character deteriorate in Buckinghamshire ; indeed the tract of country on which the Brickhills are situated, and whose rather striking escarpment faces nearly north, clothed as it is with planted pine and larch, offers a veritable oasis to the botanist, who may have been disheartened by
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