J-W Salter.
ANACHARIS Alsinastrum.
Water Thyme.
DICECIA Enneandria.
Gen. Char. Spath tubular. Flowers dioecious. Calyx
3-parted. Petals 3.—Male flower. “ Petals linear
or wanting. Stamens 9; filaments combined
into a column below.”—Female flower. Perianth
with a very long filiform tube ; segments of limb
alike. Stamens reduced to 3 subulate filaments.
Ovary inferior. Style setaceous, connate with
the perianth within the tube ; stigmas 3, notched
or lobed. Capsule 1-celled, few-seeded.
Spec. Char. Leaves 3 in a whorl, oblong, bluntish,
serrulate. Female flower in a tubular bifid spath,
subtended by a floral leaf. Perianth of broad
nearly equal segments. Germen sessile, many
times shorter than the spath. Stigmas reflexed.
Syn. Anacharis Alsinastrum. Bab. in Ann. Nat.
Hist. ser. 2. v. 1. 83. t. 8 ; Man. Br. Bot. ed. 5.
314. Hook. 8f Am. Br. FI. ed. 8. 424. Johnst.
Bot. of E. Borders, 191.
Elodea canadensis. Benth. Handb. Br. Bot. 499.
Anacharis canadensis. A. Gray, Bot. North. U.
States, ed. 2. 441 (in part).
A p p a r e n t l y there is no reason to doubt that this
plant was introduced to the canal basins at Foxton, near
Market Harborough, with timber from N. America, shortly
before the year 1847- But it had been noticed in the lake at
Dunse Castle, in Berwickshire, by the late Dr. G. Johnston,
in 1842. See Marshall’s ‘New Water-Weed’ in the Phyto-
logist, v. 4. 706 (also published as a separate tract), where a
full account is given of the discovery and dissemination of
the plant. It has spread over nearly the whole kingdom, and
is now extending its range to the European continent. In a
very few years from its first appearance, it almost choked
up the navigable canals and slower rivers, and especially the
ditches in the Fens; but of late years its quantity has very
considerably decreased; and it seems about to cease from
being the great pest of our waters.
Although only the female plant is found in this country,
and consequently no seeds are produced, the plant spreads
with almost inconceivable rapidity by the fracture of its stems
into short pieces, all of which produce independent plants.