398 THE CALLITRICHE FAMILY. 
oblong, 1 to 6 lines long, or the lower submerged ones narrow-linear, and 
obtuse or notched at the top; the upper ones obovate, and spreading 
in little tufts on the surface of the water, or all submerged and linear. 
Flowers minute, usually solitary in each axil, between 2 minute bracts vary- 
ing much in size and sometimes wholly wanting. Male flowers consisting 
of asingle stamen with a conspicuous filament ; the females of a sessile 
or stalked ovary, with 2 erect or recurved styles. Fruit from 4 to 1 line 
in diameter, the lobes either rounded or keeled or winged on the edge. 
In shallow waters or wet mud, dispersed all over the globe. Abund- 
ant in Britain. Fl. the whole season. It has been variously divided into 
from 2 to about 20 supposed species, from slight differences in the size 
and form of the fruits, the direction of the styles, in the bracts, &c., or 
from the presence or absence of the upper obovate leaves; but the 
distinctive characters which have been given all fail when applied to a 
large number of specimens collected in different parts of the world. 
[The British forms generally recognised as species or varieties are six, 
of which the first five have usually floating leaves; bracteate flowers. 
and the fruit-lobes broadly connate. 
a. C. verna, Linn. (aquatica, Sm.). Fruit subsessile, its lobes turgid, 
sharply keeled. | 
b. C. platycarpa, Kuetz. Fruit large, subsessile, its lobes flattish, 
sharply keeled. Often grows prostrate on mud, and is the C. stagnalis, 
Scop. 
ce. C. hamulata, Kuetz. Fruit subsessile, its lobes flattish, shortly 
broadly keeled. 
d. C. obtusangula, Lag. Fruit subsessile, its lobes turgid, back 
obtusely trigonous. 
e. C. pedunculata, DC. Leaves linear. Fruit sessile or stalked, its 
lobes flattish, sharply keeled. 
f. C. autumnalis, Linn. Leaves all submerged and linear, truncate. 
Fruit larger, stalked or sessile, its lobes keeled or winged, connate only 
at the axis. Rare and local.] 
LXXI. URTICACEA. THE NETTLE FAMILY. 
Herbs, or, in exotic genera, trees or shrubs, with leaves 
usually rough or stinging, more or less conspicuous stipules, and 
small, herbaceous, unisexual flowers. Perianth in the males 
regular and simple. Stamens as many as segments of the peri- 
anth and opposite to them, or rarely fewer. /Perianth of the 
females often less divided. Ovary free or rarely adherent to 
the perianth, with a single ovule, and 1 or 2 styles or stigmas. 
Fruit small, l-seeded, dry or rarely succulent. Seed with or 
without albumen, the radicle pointing upwards. 
A very large Order, chiefly tropical, of which the few British species 
give a very inadequate idea. It is readily distinguished from Euphor- 
biacee by the single-seeded fruit, from Amentacee by the regular penaa 
of the male flowers. 
