New Charophyte (Stonewort) records
K.J.ADAMS
School of Biosciences, University of East London E15 4LZ.
The following records have been added to the data base during 2001.
Nitella mucronata var. mucronata/var. gracillima
TL(52)60 680,040 18
Hylands Park, Writtle, abundant in the centre of the long pond just south of Home Farm, under blanket
of Lemna minuta, dense mats with main axes up to 10cm x 1.0mm, older parts blackish green, young
tips translucent bright green, branches mostly twice forked, with two or three two-celled dactyls.
Penultimate dactyl cells bluntly rounded, with terminal cell forming a mucro about x0.25 of the diameter
of the former, very narrow and cylindrical, tapering to a fine point, just visible to the naked eye. 17 June
2001. Peter & Pamela Wilson and Kenneth J Adams. Material kept indoors in a dish produced new
delicate pale green fertile shoots by mid-July, with richly branched nests of oogonia/antheridia bearing
branches, the former developing first. This material seemed to be of a similar phenotype to that found
in the River Stort. Most of the dactyl apices being terminated by a tiny pointed cell as in (a), with a few
exhibiting the other forms shown in the top row of Fig. 1. Kept in a glass container indoors, however,
by mid October 2002 these plants had became very fine and richly branched withthe main axes no
more than 2cm x 0.2mm and with most of the dactyl apices taking on the gradually tapered 2-3 celled-
dactyl morphology characteristic of the var. gracillima [see bottom row Fig. 1]. At the same time they
also developed copious male and female gametangia. Material collected from the wild from Bourne
Pond, Colchester in October 2002 was also fruiting and had exactly the same morphology. It would thus
seem that the two supposed varieties of N. mucronata are one and the same genetically, and that they are
simply ccomorphs of the same taxon. Responding, presumably, to the change in day length by switching
from the 'mucronata' to the 'gracillima' morphology as the days shorten in the autumn.
Fig. 1. Dactyl apices of Nitella
mucronata in summer (top row)
and late autumn (bottom row).
Chara globularis var. globularis
TL(52)92 930,233 19
Copford, the large (westernmost) pond in Gravel Pit Wood, abundant in dense mats, very large blackish-
green material with main axes up to 0.8 x 75 mm, ripe oogonia and antheridia present, primary and twin
secondary cortcxrows equal in diameter and spine cells flat 7 July 2000. Collected: Peter & Pam
Wilson, det; KJA.
(.8
Essex Naturalist (New Series) 19 (2002)