2. The Eocene between Darent and Medway, including the Hoo Hundred.

The chalk comes to the surface so near to the Thames estuary in places, and the line of the outcrop is so irregular, that the tract of country between Dartford and Rochester covered by Eocene deposits is very irregular and ill-defined. Very roughly, the Swanley Junction to Rochester railway line is the southern boundary. The exposed formations are the Lower London Tertiaries mentioned as occurring in District 1 (Metropolitan Area), but the range of habitats is less varied and, generally, the district is not good bryological country.

The few woods are varied. In the west, Darenth and Swanscombe woods are mainly on London Clay, although parts are on Thanet Beds. Originally oak-hornbeam woods, there are large areas of poor derelict woodland now. Bryophytes are a little richer than in the Orpington London Clay woods, but are not very striking. One or two elder scrub areas have the typical epiphytes of these trees – Orthotrichum affine, Schrad., 0. diaphanum, Schrad., Zygodon viridissimus, (Dicks.), R. Br., Bryum capillare, L. Amblystegium serpens, (L.), B. S. et G., Brachythecium velutinum, (L.) , B. S. et G. and B. rutabulum, (L. ), B .S. et G., - but they are less good than elder scrub in some of the disused chalk pits on the North Downs, or areas on the ragstone or Hastings Beds. Swanscombe Wood is the only recorded Kent station for Epipterygium tozeri, (Grev.), Lindb., found by Revd. C. A. Johns and recorded by Wilson in Bryol. Brit., 1855.

The extensive Cobham Woods are largely on Pebble Beds, but there are fair areas on Thanet Sand, and some of Shorne Wood is on London Clay. The clay area in this wood is characterised by several large ponds, and where roadhouse bathing pools have not been made, I have found Mnium punctatum, L. and Leptodictyum riparium (L.), Warnst. on their banks. The oak woodland on clay has nothing of particular note.

The gravel and sand areas are oak-chestnut woodland, with a few small ash-hazel areas in depressions where the chalk is probably near the surface. Ground mosses are those typical of acid woodland, including Mnium hornum, L., Catharinea undulata, (L. ), Web. et Mohr, Dicranella heteromalla, (L.) ,Schp., Plagiothecium denticulatum, (L.), B. S. et G. and Oxyrrhynchium praelongum (Hedw.), Warnst. Leucobryum glaucum, (L.), Schp. is found, (it is also in Darenth Wood), but is not so luxuriant as in the Farningham or Littlebourne woods. Nor have I found good, loamy rides with shallow, almost vertical, marginal banks so typical of woodland on clay-with-flints, and which might be expected in the Thanet sand woodland here.

Chestnut stool mosses are quite good. Aulacomnium androgynum, (L.), Schwaegr. is, perhaps, more common here than elsewhere except in the Blean, although it is not rare in many other places. Certainly it is abundant in these woods. Plagiotheciella latebricola, (Wils.), Fleisch is a frequent moss on rotting stools throughout the whole of North Kent, including these woods. Sometimes gemmae are present, sometimes not. Other stool mosses commonly found are Hypnum cupressiforme, L., Georgia pellucida, (L.), Rabenh., Plagiothecium denticulatum, (L.), R.S. et G., Dicranella heteromalla, (L.), Schp. and Mnium hornum. L. Orthodicranum montanum, (Hedw.), Loesk. and O. flagellare, (Hedw.), Loesk. have not yet been found in this area.

Stooled ash trees have the typical mosses, including Homalia trichomanoides, (Schreb.), B.S. et G., Isothecium myosuroides, (L.), Brid. and Rhynchostegium confertum, (Dicks.), B.S. et G. There is very little woodland in Hoo, and what there is is mainly on Thanet Sand and similar bryologically to the Cobham Woods.

Heaths are almost non-existent in the area. Some of the Cobham Woods have heathy clearings, and Shorne Common Roughs is, perhaps, the best example. This is very thin Pebble Beds over Thanet Sand, and the sand has been dug, leaving irregular pits. Ceratodon purpureus, (L.), Brid. is abundant; Mniurn rostratum, Schrad. and Brachythecium velutinum, (L. ),B.S.et G. are common in light shade; and along compacted tracks Barbula convolute, Hedw. and Bryum argenteum, L. are found.

Small Calluna areas at Cobham have Hypnum cupressiforme, L., var. ericetorum, B.S. et G. and Pseudoscleropodium purum, (L.), Fleisch. common, with Dicranum scoparium, (L.), Hedw. frequent.

I do not know of any boggy places, but it is possible that tiny wet areas, capable of supporting sphagna, exist, but have been overlooked.

The area has a long coastline on both the Thames and Medway estuaries. Unfortunately large areas are alluvial salt-marsh or estuarine marsh grazing, which are unattractive to the bryologist. The ditches are usually monotonous with Arundo the dominant plant. Occasionally Cratoneurum filicinum, (L.), Roth, Calliergonella cuspidata, (L.), Loesk, or Drepanocladus aduncus, (Hedw.), Moenkm. may be found at the margins, but mosses are not common. Along some ditches, where there are bare, vertical, wet-soil banks, Didymodon tophaceus, (Brid.), Jur. grows sparingly. Possibly it is the alkaline clays which support it, but it is quite widespread along the Kent coast in positions similar to this, from here to Rye Harbour.

Turf-covered sea walls run for most of the way along this coast. These have a few more mosses. Brachythecium albicans, (Neck.), B.S et G. is common; Pottia truncatula, (L.), Lindb., Phascum acaulon, L., Bryum argenteum, L. and Barbula unguiculata, (Huds.) Hedw. are frequent; locally Rhynchostegium megapolitanum, (Bland.), B.S. et G. is round in some quantity and Bryum erythrocarpum, Schwaegr. is occasional. Wherever there is stonework such as concrete reinforcement or stone filling, Tortula muralis, (L.),Hedw. is common. Similar sea-walls in Essex and Suffolk have Pottia heimii, (Hedw.), B.S. et G., and closer search might result in finding it here.

The Dartford marshes are somewhat peaty, but such land is cultivated right up to the sea-wall, mainly for market garden crops. Such cultivations preclude mosses.

Oil dumps at Grain and Stoke, explosives works at Cooling, artillery ranges at Shorne and dock and factory areas at Gravesend, Northfleet, Swanscombe, Greenhithe and Dartford, all make access to parts of the coast difficult, but it is probable that the areas thus closed would be uninteresting.

A fine shell-sand beach is found at Grain, and a smaller one at Allhallows. Tortula ruraliforrnis, (Besch.), Dix., Tortella flavovirens, (Bruch), Broth., Brachythecium albicans, (Neck.), B. S. et G., Ceratodon purpureus, (L.), Brid., Hypnum cupsressiforme L., Bryum pendulum, (Hornsch.), Schp., B. capillare, L. and Rhynchostegium megapolitanum, (Bland.), B.S. et G. are all found here.

Arable land is generally well-cultivated. Hoo is noted for its early potatoes, broccoli and other vegetable crops, and market gardening with intensive arable farming, and orchards where the soil is suitable, is the common farming type. Mosses get little chance under such conditions, but where allowed to grow, Pottia truncatula, (L.), Lindb., Bryum erythrocarpum, Schwaegr. and Barbula unguiculata, (Huds.), Hedw. are the common species. This is similar to all the Thanet Sand and brickearth areas in North Kent.

There are no rivers in the area and rock exposures are limited to the chalk. Sand pits are few, and that mentioned at Shorne Common Roughs is typical.

Chalk pits and cuttings are extensive and widespread. The much-quarried area in the neighbourhood of the cement works between Dartford and Gravesend is more properly part of the chalk area lying to the south. I have not studied it in detail, but probably it is a rather starved habitat type similar to the Downs to the south. The large pits would be worth studying. Historically the area is of interest, as both Ray and Hudson made several early records from the chalk "inter Northfleet and Gravesend". Their Thuidium species are probably all referable to Abietinella hystricosa, (Mitt.), Broth., which, in their times had not yet been described.

Except for a few isolated habitats, such as the Grain shell-sand beach, the area is not very interesting to the bryologist, but closer searching would extend our knowledge of the range of species to be found here.

Page maintained by Susan Laflin in memory of her father Thomas Laflin
Last updated January 2005.