BBS SE & Kent Field Club joint meeting, Vice-county 16, 11 March 2017

This was a joint meeting of the Kent Field Club and the British Bryological Society south-east group with the kind permission of the owner of Hungershall Rocks, Ann Preston. Hungershall Rocks sits just within Vice-county 16 West Kent and forms a small valley lined by sandstone crags.  The valley faces the more famous High Rocks and Friezland Wood just across the Vice-county border in East Sussex.  There are bryophyte records for Hungershall Rocks dating back to the 1830s and the Kent Field Club last held a meeting at the site in 1963.  Despite some catastrophic changes to the site from Victorian times, including the destruction of the ghyll stream and grubbing of the woodland, the sandstone crags persist and still retain a humid microclimate suitable for bryophytes and ferns.  Bryologically speaking Hungershall Rocks is now the richest sand rock habitat in Vice-county 16 and this meeting was a great opportunity to see the special species present.

From High Rocks car park, we walked the short distance to the entrance gate on Tea Garden Lane. The first task was to search for Scapania gracilis on a large isolated boulder near the entrance, the only recorded site in Vice-county 16.

Boulder site of Barbilophozia attenuata and Scapania gracilis

The search was unsuccessful but a consolation for the group was examining the attenuated shoots of Barbilophozia attenuata growing over the west face of the boulder.  The failure to re-find S. gracilis was rectified shortly afterward on a re-visit by myself and Sue Rubinstein.  A large patch of S. gracilis was found growing with B. attenuata close to the top of the boulder on the narrow north face, well above head height but with access helpfully provided by a small tree.  S. gracilis has persisted at Hungershall Rocks for over 60 years, since its discovery by Francis Rose in 1949.

Scapania gracilis and Barbilophozia attenuata

Moving along the sandstone crags on the western side, the group pondered over patches of Calypogeia liverworts, which on examination proved to be Calypogeia muelleriana, displaying notches to their underleaves.  David Streeter drew attention to more patches which looked more opaque which Jan Hendey later identified as Calypogeia integristipula, the rarer sand rock species of the High Weald, which lacks a notch to its underleaves.

Aulacomnium androgynum with its distinctive gemmae bearing shoots was found growing directly on the rock face by Pete Howarth, rather than its more usual dead wood habitat.  Cephalozia lunulifolia was widespread on the rocks but Cephalozia connivens with its larger leaf cells was generally less obvious, except on some shady rocks along the eastern side where it formed dense patches.  Numerous colonies of Killarney Fern Trichomanes speciosum in its gametophyte generation are present across the site, where it was discovered new to Kent last year and the group examined one of the more accessible colonies in a small cave.

On reaching a large open cave, some of the group climbed up to its roof, where at the junction with the back wall they found the moss Tetrodontium brownianum, producing a ‘lawn’ of protonemal leaves.  This specialist cave roof moss of the west and north of Britain has outlying colonies in the High Weald.  The Hungershall colony was discovered by the Kent Field Club in 1963 which re-established it then as a Kent species.  Unlike the 1963 meeting we did not find T. brownianum with any capsules, which is more typical for High Weald colonies.  A second Vice-county 16 site for T. brownianum was discovered in 2017 at nearby Avery’s Wood, near Speldhurst.

The group moved along to a section of north east facing rocks which were flushed/dripping wet in places.  This particular area is suspected as one of the two former Vice-county 16 sites for Tunbridge Filmy-fern Hymenophyllum tunbrigense, from a description by Edward Newman in his 1854 ‘A History of British Ferns’.  A lack of the filmy-fern was made up for by the rich bryophyte flora and a fine colony of Hard Shield-fern Polystichum aculeatum.  Notable bryophytes found in this habitat were Riccardia multifida, Pellia endiviifolia, Jungermannia pumila, Dichodontium pellucidum, Didymodon insulanus, Eucladium verticillatum, Fissidens pusillus, Hookeria lucens, Oxyrrhynchium pumilum and Thamnobryum alopecurum.  David Streeter drew my attention to a moss growing on a flushed rock face which was suspected to be Sciuro-hypnum plumosum, which was last recorded at Hungershall Rocks in the 19th Century.  However the specimen collected was later determined by Tom Ottley as the superficially similar Hygrohypnum luridum, first recorded in West Kent by Tom also in 2016 from a nearby Tunbridge Wells site.  This and other species from the flushed rocks indicated the base rich nature of the habitat.

Hygrohypnum luridum

Lunch was taken at the wooded northern limit of the rocks, just where the ghyll stream enters a culvert and is piped underground.  Sheltered rocks here produced the tiny pleurocarp moss Heterocladium heteropterum var. flaccidum, as well as the slightly larger var. heteropterum, along with more gametophyte of Killarney Fern Trichomanes speciosum.  Epiphytes here on Hazel Corylus avellana included the moss Ulota phyllantha and the liverwort Metzgeria consanguinea. The moss Tortula marginata was found on the brickwork of the culvert.

Sue Rubinstein searched a rock outcropping above the eastern side of the ghyll stream and discovered dense patches of a curious capsule producing liverwort which no one at the time could identify.  Subsequent examination of collected specimens were confirmed as Marsupella emarginata var. emarginata.

Marsupella emarginata var. emarginata

This was the first record of M. emarginata at Hungershall Rocks, although there is a published record from nearby Rusthall Common rocks within Edward Jenner’s 1845 Flora of Tunbridge Wells.  More common in the north and west of Britain, it has been found at widely scattered sites in South-east England and was last recorded from Kent in 1987.  On my return visit with Sue we found it to be well established on another rock nearby.

Heterocladium heteropterum and Marsupella emarginata var. emarginata

After lunch the group made its way back to the entrance gate along the eastern rock face, where many of the notable species already seen were found again.

An interesting follow-up to this meeting was the possible discovery of the nationally rare liverwort Pallavicinia lyellii. A potential fragment of P. lyellii was collected at the meeting by Sue Rubinstein from a ledge along the western rock face.  There was not enough of the specimen to establish its identity as P. lyellii.  Investigations showed that published Kent bryophyte floras lack records for P. lyellii at Hungershall Rocks, but there are published records in Sussex bryophyte floras that specifically describe P. lyellii at Hungershall Rocks, the earliest dating back to 1834.  The name Hungershall Rocks has been used since at least the 19th Century to describe the site in Vice-county 16, but Ian Beavis at Tunbridge Wells Museum showed that the name Hungershall Rocks was also used in the 19th Century to describe High Rocks and Friezland Wood.  Therefore it is open to debate whether the historic P. lyellii records from Hungershall Rocks were found in Vice-county 14 or Vice-county 16.  Sue and myself failed to find a specimen of P. lyellii on our follow up visit, so the question of its presence, both current and historic, remains to be proved.

[See also: James McCulloch. “A corner of County Kerry in a Kentish Cave” Blog post. Only Natural. 13 March 2017. Web. <https://jiainmac.wordpress.com/2017/03/13/a-corner-of-county-kerry-in-a-kentish-cave/>]