262 THE ESSEX FIELD CLUB.
two stamens and from one to four ovaries, enclosed in a sheath and produced on
the under edge of the frond.
"Two of the Batrachian Ranunculi are very common in the marshes. One—
heterophyllus—with a few floating reniform leaves, with the lower one submerged,
multifid, with filiform segments. The other —tricophyllus—has all the leaves
submerged, and smaller flowers. Flowers of both are white and float on the
surface when expanded. These are very variable and confusing plants, no two
botanists being, apparently, agreed about the nomenclature. They are said to
be destitute of the acrid and poisonous properties of the terrestrial species—the
common Buttercups.
" The above are the commonest aquatic plants which we have found in the
dykes and drains which intersect the marshes, and I will add a few remarks, which
may not be scientific, but which may possibly help the searcher after aquatic
mollusca and microscopic algae abounding in these ditches. Experience has
taught me, that the examination of the water weeds often affords a valuable clue
to the mollusca most likely to be found existing there, and they, too, also vary as
to their preference of brackish or fresh water, while others can manage to exist
indifferently in either. Amongst the pond-weeds previously mentioned, the
following forms, to the best of my recollection, thrive equally well in fresh-water
ditches and in those that are slightly brackish : viz., Potamogeton and Lemna minor,
or the Smaller Duckweed. The Ivy-leaf Duckweed (Lemna trisulca) and the
American Pond-weed (Anacharis alsinastrum) seem to favour a fresh-water
habitat, and in aquaria I have found they invariably die off if submerged in
water that is at all brackish.
" An aquatic weed, abundant in the ditches inhabited by our new Hydrobia, is, I
believe, the Horn-wort (Ceratophyllum). An Alga, which I take to be Entero-
morpha intestinalis, is very abundant in the marshes on both sides of the river.
" The ditches upon the marshes are of course a favourite hunting-ground for the
microscopist, abounding with the following minute Algae :—Nostoe caeruleum, in
immense jelly-like masses; Scenedesmus and Pediastrum ; Desmidieae of the
genus Micrasterias and Cosmarium abound, with innumerable shoals of Diatoms,
amongst which I have frequently noticed Pinnularia major and P. viridis ; quite
a number of species of Navicular, Orthosia and Fragilaria. Spirogyra also may
be taken here, but, to my thinking, it is not nearly so abundant as in many other
fresh-water localities.
" In the future, I hope to devote more time and attention to the very
interesting study of these aquatic plants, and particularly to the microscopic
alga? of the Thames marshes."
Mr. Monckton kindly read for the author, Mr. French, of Felstead, a paper
"On the Occurrence of Westleton Beds in parts of North-west Essex" (ante, pp.
210-217). Mr. Monckton made some remarks on the paper, which, together with
a note from Mr. Dalton, are printed at the end of the paper (E.N., pp. 217, 218).
Cordial votes of thanks were accorded to Mr. Monckton and to the authors of
the papers, and the meeting ended with the usual conversazione, at which Mr.
Jenkins' fine collection of Mollusca was examined with much interest.
Ordinary Meeting, Saturday, November 28th, 1891.
The 129th Ordinary Meeting was held (by the kind permission of the Rev.
W. Linton Wilson) in the hall of St. John's College, Loughton, at half-past six
o'clock, Prof. R, Meldola, F.R.S., Vice-President, in the chair.
Extracts from a paper by Mr. French, "On some Ancient Lake-Remains at
Felstead, with Notes on some similar Remains in the District," were read by the
Secretary (the full text of the paper will be published in a succeeding number of
the Essex Naturalist). .
Remarks upon the paper were made by Prof. Meldola and Mr. W. Cole, and
a vote of thanks was returned to the author.