contraria

ESSEX BOTANY AND MYCOLOGY GROUPS

The Essex Records 1820 -2007.

Following the introductory paragraph to each taxon, the records are set out in columns. The first being the letter and alternative number (in brackets) code for the 100 x 100km square, followed by the 10 x 10km square number, arranged in conventional order from south to north, moving from west to east; the second column gives the 1 x 1km square or the 100 x 100m square Ordnance Survey grid reference if known; the third the vice county, and the final column the available details of the individual record. Approximate grid references for older records are suffixed by a?

Chara contraria (A.Braun ex Kutz.)

Formerly regarded as a separate species, this taxon was demoted to being a variety of C. vulgaris (Moore et al (1986), though Stewart & Church (1992) still regarded C. contraria as a "good" species. The only stated definitive difference between this form, and the other varieties of C. vulgaris, is that its primary spine-bearing cortical rows are supposed to be prominent and the secondary rows recessive; - so that the spines appear to arise from ridges (c.f. the other C. vulgaris varieties in which they appear to arise from the grooves). Guy Allen in his British Stoneworts (1950), also claimed a correlation between the inequality of the two circlets of stipulodes and primary row dominance, and used it empirically as a means of separating pressed material of C. vulgaris sensu stricto, from C. contraria. Moore et al (1986), however, regard the relative prominence of the primary, as opposed to secondary rows as being a variable character not worthy of a specific difference. This variety is also supposed to be usually heavily encrusted, but the two of the Essex specimens I have seen were not. We have had both typical var.'contraria' and var. 'hispidula' plants in Essex, and as noted by Groves and Bullock-Webster the ripe oospores have been black as opposed to the brown of typical C. vulgaris forms. This character is best seen in alcohol-pickled material when everything except the oospores becomes transparent and the difference in oospore colouring is unmistakeable. In both the occurrences of var. 'hispidula' in Essex, material when grown on in culture has reverted to var. 'contraria' with vestigial spine cells. Although the young shoots often have the spine cells sunk in the grooves, older segments with a well developed cortex have the spine cells arising from the ridges.

Thus in conclusion I feel that C. contraria is a good species in which the spine cells of mature fully corticated segments arise from the cortical ridges and the oospores are black. As in the case of the supposed C. vulgaris varieties, var. hispidula and var. contraria are not genetically distinct but are interchangeable ecomorphs. There varietal status is therefore illegitimate.

TQ38	3940,8886	18	Walthamstow, Leyton Flats, Hollow Ponds, NE bay with Potamogeton trichodes. Fertile with globules and black oospores, 27 August 2015. K.J.Adams.
TL(52) 30	38 ,06	19	Nazeingbury Mead, flooded gravel pit, 1965, Eric Saunders.	Flora of Essex. p.45 1974.
TQ(51)49	415,871	18	Wanstead Park, Heronry Pond, abundant, eastern end. Spine cells well developed, pointed, all on raised rows, but less than axis diameter in length. Globules and nucules present. 28 July 2012. Coll: & det: K.J.Adams.
TL(52)41	493,168	19	Near Tednambury Lock, Herts. (close to Essex border), shallow recently cleared ditch, growing with Groenlandia densa, 15 August 1980. Coll: & det: by K.J. Adams.
TQ(51)57	598,790	18	South Stifford, Warren Farm Chalk Quarry, forming dense mats in water bodies in southern part of the pit. Bracts and bracteoles short as in var. vulgaris but spine cells very abundant and crowded. to twice diameter of axis in length, long-tapering, pointed and spreading. Plants collected in early July by Tim Pyner, had the spines arising from the cortex ridges, and had black oospores. Material collected on 26 July 1999 KJA) also had black oospores, and the same long crowded spreading non-deciduous spine cells, but they arose only on the sunken cortex rows. Both forms come within the variety hispidula, as defined by Moore et al (1986)
TL(52) 52	586,233	19	Chara vulgaris var. hispidula/var. contraria Easton Airfield. Two year-old pond newly excavated in the chalk. Plants bright green, unencrusted, oospores shiny black, spine cells densely clustered and overlapping, particularly just below and just above the nodes, long straight and pointed, many arising from the ridges but some clearly arising from the grooves. Some appeared to simply be the upturned tips of cortical rows that had not been cut off as separate cells. Stipuloides about equally developed to upper slightly smaller. Bracteoles and bract cells about the same as typical var. vulgaris. Spine cells on older stems much smaller and papillata-like. Antheridia, oogonia and ripe oospores present. 17 Sept 1999. Found by Shirley & Charles Watson. [N.B. when grown on indoors in tap water (KJA) this material grew vigorously but lost its long spines, and the new shoots took on the morphology of classical Chara contraria, with knob-like spine cells arising only from the ridges. Thus, as in the case of the C. vulgaris s.s. 'varieties' var. contraria and var. hispidula cannot be separate genetically defined varieties and are simply environmentally induced ecomorphs of the same taxon.]
TQ(51)67	6086,7902	18	Grays, Grays Chalk Quarry, small pond in woodland, abundant with globules, nucules and ripe black oospores. Spine cells vestigial. 17 July 2014. K. J. Adams.
TL(52)63	620,330	19	Centre of West Wood, Lt.Sampford, c.fr. November 1977. Coll: Robert J.Turner, det: K.J.Adams.
TL(52)81	835,157	19	Witham C.P. Coleman's Farm Quarry. 20 August 2022. Coll: Martin Heywood, Det: Ken Adams	var. hispidula