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Rh etc., and I have seen there also Antbriscus Cerefolium = (Cerefolium sativum), the henbane (Hyos-cyamus niger) and Bunias.

This is the counterpart to a great extent of the Colne district, ' No. 4. The Colne,' of Pryor's Flora of Hertfordshire and of the districts ' No. I. The Upper Colne ' and ' No. 2. The Lower Colne ' of Trimen and Dyer's Flora of Middlesex. The Buckinghamshire district of the Colne admits of being further subdivided into the portion drained by the Chess, and then of separating more or less artificially the Upper Colne, as is done in the Flora of Middlesex, from the Lower Colne by a line drawn across it from Uxbridge to Langley, but as the Chess and Colne are combined in the Hertfordshire Flora, and as the portion correspond- ing to the Lower Colne of the Middlesex Flora is only of very small extent, it has not been adopted here, although there is a marked difference in the physical features of the country below and above Denham.

The boundary of the district is as follows : Starting from Hampden in the middle of the county it is limited by the southern border of the Thame district, already described, by the water parting of that stream and those of the feeders of the Misbourne and Chess as far as the Hertfordshire border near Tring Park. From that place the county boundary is followed in its artificial and sinuous course by Cholebury, Kingshill, and leaving Bovingdon to the north-west, it proceeds to the picturesquely situated Latimers, and follows the charming Chess stream to Chenies and Sarrat Bottom, when it turns to Chorley Wood station, and in its southern course touches Newlands and Horn Hill, and reaches the Colne opposite to Harefield, where the Middlesex county boundary replaces that of Hertfordshire. From this place one of the anastomosing streams of the Colne is followed to Denham, Uxbridge, Cowley and Colnbrook, so named after the stream ; then leaving Horton with its Miltonian memories to the right, it joins the Thames near Staines. For about three miles the opposite side of the Thames is the border of the county of Surrey ; but at Runnymede, Berkshire replaces Surrey, and the boundary of the Colne district is circumscribed by the district of the Thames, the border line which is traced by Langley Park to the west of Fulmer, and in its northward course passes above the Chalfonts to Penn Wood, Prestwood and Hampden.

As we have seen, this district has three main drainage areas, that of the Misbourne, which flows through the Missenden valley, forming the ornamental waters of Great Missen- den Park and Shardeloes, and passing Amersham and the Chalfonts joins the Colne at Denham. The second is the portion drained by the Chess, which originates in the Cretaceous rocks of Tring, passes through the busy little town of Chesham, and adorns the beautiful valley between Latimers and Chenies with its clear sparkling water, and leaves our county near Sarrat Bottom. At Rickmansworth in Herts the Chess enters the Colne, a stream which forms the third main drainage area of the district. This is a Hertfordshire stream rising near North Mimms, but is a navigable river when it reaches our county near Tilehouse, opposite Harefield. From this place it runs through several channels to the Thames, but despite the rather squalid and dirty country which it at times passes through in its lower reaches it retains something of its pristine clearness nearly to the last, and in places affords good trout fishing. The country comprised in the boundary line described is a varied one. In the north there are the well wooded chalk hills, where the beech woods supply one of the local industries, and where bare fields of chalk with their scanty corn crops or large turnip-fields make one regret the aboriginal turf which would to the botanist be a more agreeable and natural covering. Then there is the sudden descent to the pleasant sheltered valleys of Missenden and Chenies bordered with pleasant meadows, and on the sides orna- mented with hanging woods. Where brick-earth deposits mask the chalk, the woods are not wholly of beech, but the oak can also be found ; and when, as also happens, there are outliers of the Eocene measures there are extensive gorse commons, such as those of Amersham. Further to the south there are gravelly and sandy heaths and country where the holly is a frequent tree, such as is seen at Gold Hill or Iver. Then there is that flat tract of low lying land on the London Clay through which the streams slowly wind, where great extents of brickfields mar the scene and pollute the air, and as at Drayton, vast deposits of malodorous refuse from the London dustbins give a squalid and unpleasant appearance to the scene. There are also tracts of ground given over to the market gardener, and the whole scene contrasts very strongly and unpleasantly with that of the northern part.

There are however a large number of species found in the district, and it is the only one for which the following species have been recorded. One of these is an extremely local sedge,