ESSEX BOTANY AND MYCOLOGY

ESSEX BOTANY AND MYCOLOGY GROUPS

Riccia fluitans txt:

Riccia fluitans L. emend Lorbeer

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An aquatic light green to yellow-green liverwort found floating, often in dense masses at or just below the water surface of ponds, stagnant abandoned canals, gravel and clay pits, or scattered on mud amongst marginal vegetation in both acidic and basic mesotrophic to eutrophic waters (Hill et al). Often occurring in ponds that dry up in summer, leaving the thalli stranded. The thalli are strap-shaped, and repeatedly bifurcate at an angle of around 45^o, so that they curve back on themselves after several dichotomies. Unlike R.. rhenana, they retain their shape when stranded on mud.. They gradually increase in width towards the apices, ranging from 0.3 to 2.0mm wide and 1-5cm long . Most of the thallus consists of tiny air chambers up to 0.3mm long, with a single layer of cells above and below, and with minute pores opening to the upper surface, but in the centre the tissue is thicker below with smaller air chambers above. The apices are grooved and the surface of the straps have a reticulate appearance due to the air chambers. Semi-lunate scales occur sparsely along the mid-line on the underside, increasing in size towards the apices. Nationally it occurs mainly in the south east of England, with only scattered records for the west country, Wales and Ireland and is absent from Scotland (c.140 x 10km sq records for England and Wales). On the continent however, it extends northwards to southern Scandinavia, and is found widely in temperate Europe and Asia, extending south eastwards through Indonesia to Japan and New Zealand, and is also found in temperate North America. It can persist at the same locality for many years, the plants dying back to just the swollen apices, which sink to the bottom, and rise up again in the spring. How it spreads is a mystery. It is presumed to be dioecious, but archegonia, antheridia and sporophytes are rarely found. Sex organs apparently only develop, if at all on stranded thalli in around November time, and may therefore be overlooked. The sporophytes are embedded in the gametophyte thallus and bulge downwards as spherical swellings on the underside of the straps. Small floating thalli are probably also spread around on birds feet, so much of its dispersal, at least in Britain may be vegetative. In Essex it is widespread in occurrence, except on the chalk and boulder clays, occurring most commonly in old gravel and clay working ponds, often persisting for decades, though mysteriously failing to appear in some years. [Closely related to two other aquatic liverworts R. rhenana and R. canaliculata that occur in Britain].


ALL RECORDS
TQ(51)39		18	Chingford, Epping Forest, 1927. D.G.Catcheside.
	392,945	18	The Warren Pond, opposite Queen Elizabeth’s hunting Lodge, Epping Forest, marsh at southern end. 1985 & 1986, Kenneth J Adams.
	395,911	18	Oak Hill, Woodford, Epping Forest, the third small pond in from Oak Hill road, on marginal mud. 11 July 1970. Kenneth J Adams.

TL(52)30	398,037	19	Ponds by Galley Hill Wood. 1959. Eric Saunders.

TQ(51)49 .		18	Epping Forest, in pond attached to Utricularia. April 1942. J.H.G.Peterken.	(BBS Herbarium, National Museum of Wales, Cardiff)
.	408,941	18	Church Road Pond, Buckhurst Hill, 17 August 1967. Kenneth J Adams.
	401,957	18	Cuckoo Pits, Epping Forest 1920. Joseph Ross.	(Essex Naturalist 21: 303).
		18	Cuckoo Pits, 1950. J.H.G.Peterken.
	409,965-7	18	Fairmead Bottom Pond, Epping Forest, 1959. Eric Saunders; August 1981. Kenneth J Adams.
	409,979	18	Oak (Speakman’s) Pond, High Beach, numerous small patches on wet mud in the SW bay of drying up pond, 9 July 2004, Kenneth J Adams. Still present 30 July 2006. K J Adams. Plentiful SW margin above the Crassula helmsii zone. July 2009 and a few rosettes 29 May 2011. No sign July 2012.
	412,964	18	Strawberry Hill gravel workings, on mud 28 July 2006. K.J.Adams.
	412,964	18	Strawberry Hill gravel workings, on mud with Lemna minuta, 8 April 2022. K.J.Adams
	415,967	18	Earl’s Path Pond, Epping Forest, 1964; Alan J Harrington; 1967. Bernard T Ward; 1974. Kenneth J Adams.
	419,984	18	Lesser Wake Valley Pond East, several small, fragments amongst other vegetation. 20 July 2018. K.J.Adams.
	419,984	18	Lesser Wake Valley Pond East, several small, fragments amongst other vegetation. 29 July 2020. K.J.Adams. Pond only 10cm deep.
	422,978	18	Epping Forest, on Lost Pond delta, small colony. 18 September 2008. Kenneth J. Adams.
			Goldings Hill, Epping Forest, in one of the ponds, 1905. Essex Naturalist 14: 276.
			Golding’s Hill (upper?) Pond, November 1924. Paul W Richards; Main hepatic collection. Reg.No: 52.112.1 National Museum of Wales. Cardiff.
	428,979	18	Golding’s Hill Lower Pond, extensive floating rafts, 8 February 1987. Kenneth J Adams (present from 1981-1989).
	428,980- 429,980	18	Golding’s Hill Upper Pond, as blankets among marginal vegetation1981-1989. Kenneth J Adams;1998 Amanda Samuels.
	421,986	18	Little Valley Wake Pond, 1973, Katherine Admieka.
	455,944	18	Chigwell, pond just west of pudding lane, 1970 (now built on). Kenneth J Adams.
	47, 92	18	Hainault, Hoghill Pond, 1800. Edward Forster.
TL(52)40	40847,01746	19	Waltham Abbey, large stranded colony in centre of Cobbins Pond. 15 October 2013. Kenneth J Adams.
	42861,00720	19	Waltham Abbey, large colony stranded on margins of pond by NW corner of the Warren. 8 October 2013. Kenneth J Adams.
	419,010	19	Upshire, woodland in curved old gravel working, dried up mud, abundant, 17 Oct 2009. K J Adams & Tim Pyner.
	441,006	19	Pestle Pits Pond, Epping Forest, date? Bernard T Ward.
	442,007	19	Hawcock Pond, Epping Forest, abundant on mud and overhanging banks, no floating plants, July 1980. Kenneth J Adams.
	442,007	19	Hawcock Pond, road end under Salix cinerea. July 2005. KJA.
,	454,016	19	Bell Common Pond North, continuous carpets on mud of dried up pond, September 1986, Kenneth J Adams. (pond subsequently dredged winter1986/7 by Epping Forest Conservation Volunteers).
	47 , 03	19	Gravel Working Ponds near St. Margaret's Hospital, Epping, date 1980s, Kenneth J. Adams
,	467,077	19	Latton Common Pond, edge of Mark Bushes, on mud at southern end of pond, 22 October 1967. Janet M Adams.
	466,076	19	Small pond in Mark Bushes, 7 June 1986. Kenneth J Adams.
	481,027	19	Gernon Bushes, small pond on north side of Essex Way, floating form. 4 July 2012. Kenneth J. Adams.

TL(52)41	490,173	19	Tednambury, drainage ditch in Stort Valley, floating and terrestrial forms, 15 August 1980. Kenneth J Adams.

TL(52)50	563,009	18	Kelvedon Hatch, Great Myles lake. Terrestrial form. 11 September 1988. Kenneth J Adams et EFC.

TQ(51)58	572,855	18	Cranham Marsh, on damp clay by drain from Spring Wood to Middle Wood. 1990. Kenneth Hill.

TQ(51)59	5453,9299	18	Dagnam Park, pond in NW of Hatter's Wood, abundant. 5 May 2010. Mary Smith.
TL(52)51	52 ,15	19	Hatfield Heath, pond just north of. 1959. Eric Saunders.
	523,185	19	Gt. Hallingbury, abundant in small pond in corner of Wall Wood, just south-east of road, 1987. Shirley Watson.

TQ(51)69	601,931	18	Shenfield Common, large pond in secondary woodland, with Ricciocarpos natans, July 1987. Kenneth J Adams.
	615,907	18	The Horse Pond, Childerditch, now dried up, on mud in centre of pond with Ricciocarpos natans under Juncus effusus. 13 July 1986 Kenneth J Adams et EFC.

TL(52)60	601,042	19	Norton Heath, abundant floating raft in one large pool. 30 March 2009. K J Adams. Still present 2010. Absent from pools now carpeted by Lemna minuta, but few scraps on damp mud of shallow hollow. 17 July 2014.

TL(52)70	780,036	18	Danbury, Backwarden, in old gravel working, abundant as terrestrial form on rotting leaves, 4 October. 1993. Tim Pyner

TL(52)71	757,114	19	Boreham, old gravel pit, narrow floating form, 10 November 1986. Tim Pyner. Still there October 2011. Barbara Chapman.

TL(52)81	85 ,11	19	Great Totham, old gravel workings, terrestrial form on damp soil under Salix. 3 August 2002. Tim Pyner.

TL(52)83	85 ,35	19	Pond in Twinstead Wood, 1966. Peter J Wanstall.
	88 ,37	19	Lamarsh, Daws Hall, abundant in drainage ditch, 23 August 1981, Kenneth J Adams.

TL(52)91	91,18	19	Layer Marney C.P. Layer Wood, small pond in NW corner. 2003. Peter Wilson.
	9145,1783	19	Layer Marney C.P. Layer Wood, on mud by pond in SE corner. 15 December 2013. Marion Miller et Essex Bryology Group.

TL(52)92		19	Layer Marney, 1861. Dr Ezekiel G Varenne.	Essex Naturalist 22: 76.
	950,221	19	Warren Plantation, eutrophic marsh opposite Colchester Zoo, 1968. Kenneth J Adams.
	9821,2123	19	Colchester, Friday Wood, terrestrial form banks of small pond. W. Chisholm et CNHS. 27 November 2012.

TM(62)01	04 ,19	19	Fingringhoe Wick N.R., floating form in pond by Arch Hall, 1969. Stanley T Jermyn.
			Fingringhoe Wick N.R., floating form in dense rafts, pond near the entrance and in the winter wet ponds, 8 September 1979. Kenneth J Adams.
			Fingringhoe Wick N.R., more or less permanent in the gravel working ponds at the Wick. Present in quantity in the Sand Martin Cliff pool October 1991. Kenneth J Adams& Tim Pyner. Only a few scraps in Bunkhouse Pool 2005. K J Adams

TM(62)02	025,212	19	Rowhedge Pits, small gravel working. 14 April 1982. Kenneth J Adams
	028,204	19	Fingringhoe Village Pond, 2002. Peter Wilson.
.	031,293	19	nr. Ardleigh Reservoir, 1987. Bill Chisholm.
	031,293	19	In narrow moat, plentiful, northern edge of small copse, Ardleigh. 5 February. c.2009 Kenneth J Adams.
	025,289	19	nr. Ardleigh Reservoir, 1987. Bill Chisholm.