152 ON A NEW BRITISH ALGA FOUND NEAR MALDON.
Maldon this is not the case, the antheridia being found on separate
individuals. By L. Kolderup Rosenvinge this form has been
described as a variety. Dr. Nordstedt, however, after numerous
observations made on the young plant, concludes that it cannot be
regarded as more than a form of this variable species.1 V. sphoero-
spora is probably identical with the Vaucheria velutina, Harvey, of
which a figure is given (with the oogonium only) in "Phycologia
Britannica," vol. iv., t. cccxxi.2
Vaucheria sphoerospora, f. dioica, Nordst., grows on the shores of
muddy creeks, forming pale green matted velvety tufts visible about
a quarter of an inch above the mud. The plants are densely intricate,
and are furnished with short erect lateral ramuli. Subsequently Dr.
Nordstedt found the same plant on the muddy banks of the Thames
near Kew Bridge. I have also received it from Cornwall, in which
county it was collected by Mr. R. V. Tellam on the shady banks of
the Fowey river, half-way between Lostwithiel and Fowey, and near
highwater mark. Mr. Tellam's specimens bear the date of September
16th, 1880, and they are evidently the dioicous form of the plant.
I may add that Dr. Nordstedt has also detected the following
marine species not previously recorded, so far as I am aware,
as British plants, viz. :—Vaucheria thuretii, Woron., V. litorea,
Hoffm., V. synandra, Woron. Figures and descriptions of these
species were published in the "Scottish Naturalist" for October,
1886, in a paper entitled "Some Remarks on British Submarine
Vaucheriae."
Gravel on Northey Island, near Maldon.—On the occasion of my visit to
the Maldon railway cutting, Mr. Fitch was also good enough to drive me over to
Northey Island, which is situated about a mile and a halt south-east of Maldon,
and is shown on the geological (drift) map to be composed of about one-third
London-clay and two-thirds marsh, the London-clay being towards its south-
western end. At the northern end of the part coloured London clay, and close
to but west of, the only house on the island, Mr. Fitch pointed out a small patch
of' gravel that had escaped the notice of the geological surveyor. There was,
indeed nothing in the contour of the ground to suggest the existence of anything
beyond London-clay and marsh. The area occupied by this small deposit of old
estuarine "ravel is but a few square yards, nevertheless its existence is a matter of
some consequence to Mr. Fitch, whose land is almost wholly London clay and
marsh and who uses the gravel in road-making. And as a glance at the drift map
shows abundance of gravel immediately east of Maldon and north of the channel
of the Blackwater, and its absence from the southern side, this Northey gravel is
eminently worthy of being noted on future editions of the map simply from its
importance to agriculturists.—T. V. Holmes, F.G.S., July, 1887.
1 See Nordstedt's remarks, "Scottish Naturalist," 1886, p. 382, and my paper on "British
Marine Algae," Ibid., p. 258.
2 In this plate the lower right-hand figure with sessile oogonium is probably referable to V.
thuretii, Woronin. Nordstedt found the two species growing together near Ballachulish, one of
Harvey's localities for the plant.