R iv u la r ia echinata. {English Botany.)
Globose, very minute, dark coloured, compact. Threads
fastigiate, attenuated upvvard.s to the apex, closely cohering,
articulated, heterocysts basal, globose. Slieaths very narrow,
almost inconspicuous.
S iz e . Triohomes '007 mm. at base, -25 mni. long.
Chcetophora punctiformis, Kutz. Tab. Phyc. iii., p. 4 , t. 18, f.
2. Eabh. Alg. Eur. iii., 386.
Echinella articulata, Eiig. PI. v., p. .398. Eng. Bot. ii., t.
2655. Harv. Man. 187.
Conferva echinata, Eng. Bot. i., t. 1378.
Conferva echinulata. Gray. Arr. i., 310.
In lakes, ponds, &e.
This minute species, which was first described and figured in “ English
Botany,” appears to have been unknown on the Continent. We have
received it from several localities beside the original one of Ellesmere.
I t is one of the Algæ which are associated with the phenomenon called
“ Breaking of the meres,” thus alluded to by Professor Dickie in his
“ Botanists’ Guide’’ (p. 310) :—“ For some years excursions were made
with the students of my botanical class to a loch on the estate of Parkhill,
about four miles north-west from Aberdeen. The sheet of water in
question is about a quarter of a mile in its greatest length ; on almost all
sides it is surrounded by extensive deposits of peat, with the soluble
matter of which a great proportion of the water passing iuto the loch is
impregnated. The locality was generally visited in the beginning of
July ; nothing particular had ever been observed till the summer of 1846,
when my attention was arrested by a peculiar appearance of the water,
especially near the edge, but extending also some distance into the loch.
Numerous minute bodies, with a spherical outline, aud varying in size
from 1 24th to l-12th of an inch in diameter, were seen floating atdifferent
depths, aud giving the water a peculiar appearance. In some places
they were very densely congregated, especially in small creeks at the
edge of the loch. A quantity was collected by filtration through a piece
of cloth, and, on examination by the microscope, there could be no doubt
that the production was of a vegetable nature, and a species of Rivularia;
one, however, unknown to me, and not agreeing with the description of
any species described in works to which I had access. Specimens were
sent to the Rev. M. J. Berkeley ; he informed me that the plant belonged
to the genus mentioned, and stated it to be Rimdaria echinulata, Eng.
Bot. Along with it, but in very small quantity, I also found another
plant, Trichormus flos-aquoe, Bory.
“ In the first week of July, 1847, the same species were observed
similarly associated, bat the Trichormus was now more plentiful, with,
out, however, any apparent corresponding diminution in the quantity of
the Rivularia.
“ In July, 1848, it was observed that the R iadaria was as rare as the
Trichormus had been in 1846 ; to the latter consequently the water of
the loch now owed its colour, which was a very dull green; the colonr,
however, becomes brighter when the plant is dried. In neither of the
seasons mentioned was it in my power to make any observations on the
colour of the loch earlier or later than the date above mentioned, consequently
nothing can be added respecting the comparative development
of the two plants at other periods of the season. Other two lochs in the
vicinity did not contain the plants alluded to.’’
As these pages are being printed (July, 1884,) this alga has been sent
us from a large pond between Haslemere and Farnbam, rendering the
water quite opaque, described as “ like a mixture of pea soup and
water.” See also Bornet and Flahauit, “ Sur da determination des
Rivulaires, &c.,” in “ Bulletin de la Société Botanique de France,”
t. xxxi., p. 76 (1884).
Plate CXIV.Jig. 2. a, natural size ; b, cluster maguified ; c, trichomes
X 400 diam.
R iv u la r ia calcarea. Eng. Bot ii. ed., t. 1799.
Hemisphærical, gregarious, confluent in a very liard mamil-
lose incrusting blue-green or brownish stratum, internally repeatedly
zoned, zones of a darker green, trichomes ra th e r thick,
pale blue green, slightly flexuous, distinctly articulate, ending
at the apex in a colourless hyaline point ; sheaths narrow,
colourless or brownish at the base ; heterocysts globose, lower
joints of the trichomes equal in length to their diameter.
S iz e . Triohomes ’006 mm. diam.
Eng. Fl. V ., 392. Harv. Man. 150.
Ainactis calcarea, Kutz. Tab. Phyo. ii., t. 63, f. 11.
Litkonema calcarea, Hass. Alg. 265, t. 65, f. 2.
Zonotrichia calcarea, Rabh. Alg. Eur. ii., 213.
Linchia dura, a calcarea, Grev. PI. Edin. 322.
On rocks and stones in streams.
Plate, CXVI. fig. 3. a, section natural size ; i, portion with trichomes
X 400 diam.
R iv u la iia dura. Kutz.
About the size of a mustard seed, rather hard, dark bluish-
g’reen, becoming brownish or brackish ; triohomes æruginous,
variable in the same thallus, some thin and inarticulate, others
thicker, articulate and torulose, all with distinct sheaths,
lengthened at the apex into a colourless flexaous inartioulated
thread ; lower joints as long as broad, or nearly so, upper ones
longer, all granulated ; sheath colourless, or yellowish ; heterocysts
rounded, oblong.
S iz e . Triohomes ’OOS-'OOfl mm. diam. at the base.
Limnactis dura, Kutz. Tab. Phyc. ii., t. 64, f. 1. Rabh. Alg.
Eur. ii., 211.
Rivularia radians, var. dura, Kirch. Alg. Schles. p. 223.
Attached to aquatic plants, especially Chara.
Plate CXV.fig. 2. a, natural size , 6, section enlarged; c, trictomes
X 400 diam.