Ricciocarpos

ESSEX BOTANY AND MYCOLOGY GROUPS

Ricciocarpos natans:

Ricciocarpos natans (L.) Corder

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An unmistakeable floating liverwort of neutral to highly base-rich stagnant ponds and abandoned canals, frequently in association with Riccia fluitans. Very rare and probably decreasing in the U.K., but virtually world wide in distribution and in some countries very abundant. Not found in Scotland, 56 x 10km sq records post 1950 in England/Wales/Ireland, but it seldom persists for more than a few years at any one site, so these figures give an over estimate of its occurrence at any one time. The thalli fragment into 1-2 furcate portions, that sink to the bottom in late autumn, and rise up again in the spring, though like Riccia fluitans they may not do so every year. If the pond dries up during the growing season, the stranded thalli continue to grow, but retract their floatation scales and may narrow down their bifurcations to resemble Riccia fluitans. Sporophytes are said to be very rare in Europe and there do not seem to be any records for the U.K. It is therefore a mystery as to how it is dispersed in this country. Fragments of thalli on muddy birds feet seem the most likely source of propagules; though odd spores leading to single sex clones might be brought over in this way from parts of the world where it does produce sporophytes. In America, it is apparently monoecious, and fruits abundantly. Smith suggests that our clones may be dioecious, which might explain the lack of sporophytes. Paton however, notes that sexual organs have not been found in Britain either. Elsewhere, the antheridia and archegonia apparently occur along the mid-line of the lobes, and the sporophyte is spherical and immersed in the upper surface, the mature spores being blackish-brown. Being so uncommon a plant, it is possible that sexual organs have been overlooked. It has been exterminated on Epping Forest by the dredging of first of all Earl’s Path, and then Goldings Hill Upper Pond. Not apparently by removing all the thalli, but by changing the nutrient status of the water. It is seems likely to meet the same fate in Dagnam Park, where ponds are similarly being dredged to reinvigorate them. Fifteen 1km sq records from Essex, though it is sporadic and seldom likely to be present at more than a couple of sites in the county at any one time.


TQ(51)49	473,927	18	Hoghill Pond, Hainault. 1800	Edward Forster. Essex Naturalist
	47 ,95 ?	18	Floating in a pond between Abridge and Lambourne, 22 July 1883.	(Note penned in the margin of a reprint of the Hepatics of Suffolk (Journal of Botany 1885).
	457,944	18	Muddy bottom of hoof-holed dried up bottom of small cattle drinking pond, in mats with Riccia fluitans, by west side of Pudding Lane, Chigwell, 1970. Kenneth J Adams (this pond, one of two together, was infilled in1979, site now built on).
	42 ,92	18	Pond by Luxborough Lane, Chigwell, 1917 P J Thompson.
			In two ponds by Luxborough Lane, Chigwell, plentiful. 1926.
			D J Scourfield. Disappeared from Luxborough Lane, `some small ponds by the lane, for long the only recorded station in Essex, were searched in vain’ 1932.	Essex Nat. 24 p.54.
			Found on a foray, `new to Epping Forest’ by D J Scourfield, 1930.	Essex Naturalist 23 p140 & 142.
			Lower (Lesser?) Wake Valley Pond, 1942. J H G Peterken. Floating in a pond with Lemna trisulca and L. minor, Epping Forest. VC18 14 March 1942.	BBS Herbarium. National Museum of Wales. Cardiff.
	419,985	18	The Bomb Crater Pond, Monk Wood, Epping Forest, 1959. Eric Saunders and Bernard Tavener Ward.
	415,967	18	Earl’s Path Pond, Epping Forest, 16 Octobe1960 `fairly plentiful, southern margin’,David T Streeter, Kenneth J Adams et al (Queen Mary College Field Trip). Still present 28 October 1964; Alan J Harrington.
			Earl’s Path Pond, persisted until 1976 when the pond was scoured out down to the gravel base having dried up completely during an exceptional drought. Most of the silt was removed changing the character of the pond. According to Sylvia Boyd-Andrews a few thalli resurfaced in early June 1977 following the clean out, but they have not appeared since (Kenneth J Adams 2003).
	424,975	18	Baldwins’s Hill Pond, c.1960. recorded on large scale pond survey map found in documents derived from the then South West Essex Technical College.
	429,980	18	Goldings Hill Upper Pond. First appeared in the narrow leaf-filled channel behind the island with Riccia fluitans, 28 July 1981. Judith Adams. Later became very abundant and spread round to the other side of the pond, June 1982. Janet M Adams. In 25 May 1985 a small patch appeared in the narrow channel only. The channel was dredged over the winter of 1985/6, but a few thalli managed to surface by the 27 May 1986. Kenneth J Adams. There has been no sign of any plants, despite looking every year since. The channel was redredged in October 1991, (a single thallus appeared in 1995 south of the island) and again along with the whole pond over the winter of 2000/2001.

TL(52)40	441,006	18	Pestle Pits Pond, Epping Forest, `the one with the conduit’, plentiful one year with Riccia fluitans, Bernard Tavener Ward.date? Sometime in the 1960s].

TQ(51)59		18	Dagnam Park, a pond in, 1979. Peter J Wanstall.
	550,927 & 552,928	18	Dagnam Park, in two overgrown ponds, both at the southern end of the Park. 24 June 1979. Kenneth J Adams
	5528,9284	18	Dagnam Park, one thallus on overgrown pond to east of track. 17 June 2010. K.J.Adams
	550,927	18	Dagnam Park, mud form all over the bed of the dried up pond ,west of the north-south track. 20 July 1981. Kenneth J Adams.
	550,927	18	Dagnam park, same pond recently dredged, but still surrounded by trees. Huge population all over the surface looking like a giant Lemna. 16 July 2000. Kenneth J Adams et EFC. Same pond, still present June 2004, just a few tiny thalli floating on the surface; by 4 October numerous scale-less thalli stranded in a 1m band on the sunlit eastern side and floating plants gone. Kenneth J Adams.

TL(52)51 or 52		19	Hatfield Forest, `floating in a pond’ 18 May 1942. J H G Peterken. (BBS Herbarium Nat. Mus. Wales. Cardiff).
TL(52)51	520,176	19	Woodside Green, Great Hallingbury, floating on a pond by Lodge Farm. 1950s. E G Eagling & John L Fielding.

TL(52)52	539,209	19	Hatfield Forest, floating on a pool in the lake marsh nature reserve, 1982. John L Fielding confirmed Kenneth J Adams	[BBS Herbarium and BBS Bulletin 44. p.23].

TQ(51)69	600,935	18	Shenfield Common, on soft mud of pond margins, pond dried up and developing into secondary woodland adjoining the Common. Autumn 1985. Michael Chambers (teacher Brentwood School).
	601,932	18	Shenfield Common, plentiful, floating form in large pond in Shenfield Common woodland, with Riccia fluitans and Lemna trisulca. Kenneth J Adams et EFC. 19 July 1987.
	615,907	18	The Horse Pond, Childerditch, on mud in centre of pond, which was completely vegetated over with Riccia fluitans beneath tall herbaceous vegetation. 13 July 1986. Kenneth J Adams et EFC.

TL(52)70		18	Little Baddow. 1881. H N Dixon.