Page:VCH Buckinghamshire 1.djvu/101

Rh which once yielded ferns in plenty are now despoiled, and the primroses are becoming in turn the sufferers.

These species are well nigh extinct, but drainage and cultivation rather than the wilful marauder are the agents which have exerted malevolent influence on this genus. L. inundatum still lingers in one or two heaths in the Thames district, and L. Selago formerly grew and may still occur there, and ''L,. clavatum'' may probably be found in some of the bracken-covered areas of the Chilterns or Brickhill.

Pilularia, the only member of this order, has been found in the heathy bogs of the Thames or Colne district, but it is very easily overlooked from its minute size and grass-like appearance, and it often grows submerged, or partially submerged, on the margins of peaty ponds.

The wood horsetail (E. sylvaticum) is our rarest species, and it appears to be absent from the Brickhill woods, which look so suitable a home for it; but it is to be found in the Burnham country, although very locally.

E. maximum is locally abundant, especially in the Ouzel and Ouse districts, choosing a place where a pervious stratum rests upon a bed of clay, so that permanent moisture can be enjoyed, and then if it is shaded by trees the plant grows in great luxuriance and is of real beauty. E. limosum, and as the variety fluviatile, E. palustre and E. arvense are all common except in the chalk uplands.

These water plants having been mentioned under the various districts, a mere allusion to them will suffice. They are often of very uncertain appearance, being most abundant for a season and then disappearing for many years. The largest and most beautiful of the order, Nitella translucens, is however almost always to be seen in the ponds at Burnham Beeches; N. flexilis has been found at Brickhill and in Wilton Park, N. opaca at Eton, etc. Tolypella glomerata occurred near Castlethorpe in the Ouse, and at Brickhill in the Ouzel district. Chara hispida occurs at Brickhill, and C.fragilis var. Hediwigii in the Thames.

Further search will be certainly rewarded by the discovery of three or four more species.

Among the British counties Buckinghamshire ranks above the average in the number of its bramble forms, as in the sandy heaths and gravelly commons and woods they meet with a soil and conditions which are suitable for this very variable genus. The Greensand at Brickhill is especially rich in forms, and it is the only British home for Rubus hirtus