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 A HISTORY OF HERTFORDSHIRE CARYOPHYLLE.* Silene noctiflora, L. Arenaria (Alsine) tenuifolia, L. LEGUMINOS/E Trifolium ochroleucum, L. Astragalus hypoglottis, L. Hippocrepis comosa, L. ROSACE.S Poterium officinale, Hook. f. UMBELLIFER.* Bupleurum rotundifolium, L. Apium graveolens, L. Carum (Bunium) bulbocastanum, Koch Sesseli libanotis, Koch (Libanotis montana, CEnanthe Lachenalii, Gmel. Caucalis daucoides, L. VALERIANS* Valeriana ofHcinalis, L. COMPOSITE Antemaria dtoica, Br. Senecio (Cineraria) campestris, DC. Arctium majus, Schk. Cnicus eriophorum, Hoffin. SCROPHULARINE.S Linaria spuria, Miller Melampyrum cristatum, L. OROBANCHE^ Orobanche major, L. LABIATVE Ajuga chamxpitys, Sckreb. LORANTHACEJE Thesium linophyllum, L. (humifusum, DC.) ORCHIDEJE Orchis ustulata, L. AunucEB Aftsma ranunculoides, L. NAIADACUI Potamogeton coloratut, Hornem GRAMINEJE Bromus racemosus, L. Brachypodium pinnatum, Beauv. DISTRICT II. THE IVEL This district is south-west of that of the Cam, and is bounded on the north-west by Bedfordshire and on the south by the Lea district. The Ivel rises near Baldock, leaves our county for Bedfordshire after a run of a mile and a half, and is then soon joined by a longer stream rising near Wallington. Its next tributary is the Hiz, which rises at Wellhead, a mile south of Hitchin (Hiz-chine), through which it flows. A mile below Hitchin the Hiz receives the Purwell or Pirrall, a stream having a much longer run than itself, and rising between Weston and Graveley ; and in another mile, at Ickle- ford, it receives a small stream called the Oughton. Half-way between Bedford and St. Neots the Ivel joins the Ouse, which pursues its course for some forty miles before it receives the Cam near Ely. The Chalk downs of the eastern division of the Cam district are continued in a south- westerly direction through the Ivel district, of which they form the north-western half. Highest on the south-east, they slope downwards to the Gault plain on the north-west. Here there are numerous combes in the Lower Chalk which have been formed by water issuing from springs in the Totternhoe Stone. In most of them there is now no water and the soil is particularly dry owing to the sinking of the plane of saturation of the Chalk, this portion of the district consequently having an essentially xerophilous flora. Although this is a much larger district than that of the Cam, and its botany has been more thoroughly investigated than that of any other, only half a dozen species are restricted to it. Melampyrum arvense occurs only in one spot south of Ashwell ; Smyrnium olusatrum has been found in one or two places north of Baldock and near Pirton, and there is also a record of its occurrence at St. Albans in the Colne district, but its site has long been built over ; and the other four species are confined to the neighbourhood of Hitchin. Of these Silene conica is the rarest. The only record of its occurrence is near High Down, Hitchin, in 1875. The rarer plants of the district are RANUNCULACEJE Anemone pulsatilla, L. Ranunculus diversifolius, H. Wats. Helleborus fcetidus, L. viridis, L. PAPAVERACEJK Papaver hybridum, L. Lecocjii, Lamotte FUMARIACEJK Fumaria Boraei, Jord. parviflora, Lamk. Vaillantii, Lotsel. CRUCIFER.S Senebiera (Coronopus) didyma, Pennon Iberis amara, L,