424 | THE NAIAD FAMILY, 
Common near the sandy or muddy edges of the sea, | in temperate 
regions of the world, usually at or below low-water mark, and often 
thrown up in great quantities by the tide. Abundant round ‘the British 
Isles. Fl. summer, or, according to some, in spring only. | 
2. Z nana, Roth. (fig. 952). Dwarf G.—Closely resembles the 
smaller forms of Z. marina, of which it may be a variety. The leaves 
are usually from a few inches to near a foot long, very narrow, with 
only 1 or rarely 3 distinct nerves; the flowering sheath about half an 
_ inch long, and the flattened peduncle inside has to every ovary a little 
transverse appendage or band. Seeds shorter than in Z. marina, per- — 
fectly smooth. 
On sandy shores, usually between high- and low-water marks, in 
various parts of the world. Common in western Europe, and has been 
found on several points of the British coasts. Fl. summer and autumn. 
The seeds appear certainly distinct in the two species; the constancy 
of the other characters is doubtful. I have examined only the dwarf 
species in a living flowering state. 
II. NAIAS. NAIAD. 
Slender, branching, submerged plants, with linear, opposite or ter- 
nate, entire or toothed leaves, often crowded into whorls or clusters. 
Flowers small and sessile, often clustered with the branch-leaves in the 
axils, and dicecious or rarely moncecious; the males consisting of a 
single, nearly sessile anther, enclosed in 2 bracts; the females of a 
single ovary, sessile in the sheathing base of the leaf, with 2 to 4 sub- 
ulate stigmas. Fruit a small, seed-like drupe. Embryo straight. 
A genus of few species, widely spread over a great part of the globe. 
1. N. fiexilis, Rostk. (fig. 953). Slender. N.—Leaves narrow-linear, 
usually in whorls of 3, or sometimes opposite, often clustered in the 
axils, about 6 or 8 lines long; the teeth few and very minute. Stigmas 
usually 3, sometimes 4. Fruit oblong, about a line long. 
A common North American species, observed in a few scattered 
localities in Europe, and found in Perthshire, Skye, and Connemara 
in Ireland. fl. summer. P 
[2. N. marina, Linn. (fig. 954). Holly-leaved N.—Stems with here 
and there toothed wings. Leaves opposite and ternate, linear, strongly 
spinular-serrate. Fruit ellipsoid, + of an inch long. 
Common in the tropical and some temperate regions of the Old : 
World. In Britain, found only in Hickling Broad, Norfolk. Fl. summer. _ 
3. N. graminea, Del. (fig. 955). Grassy N.—Leaves in clusters at 
the nodes, narrowly linear, less than an inch long, serrulate. Stigmas 
2, Fruit linear- -oblong. 
A native of stagnant waters in the hotter regions of Asia, which has 
been introduced into Italy, Austria, and Lancashire. | 
Ill. ZANNICHELLIA. HORNED PONDWEED. 
A genus limited to a single species ; differing from the narrow-leaved 
Potamogetons by the moneecious flowers sessile in the axils and without — 
