Empetrum.] LXIX. EMPETRACE. 397 
stamens of the males protruding from the perianth on slender filaments. 
Fruit black, globular, about the size of a pea. 
In mountain heaths and bogs, in Europe, Asia, and North America, 
very abundant at high northern and Arctic latitudes, and quite alpine in 
southern Europe and central Asia, and a-red-berried variety abounds in 
the Falkland Islands. Common in Scotland, in northern and western 
England, and in Ireland. /l. spring. 
LXX. CALLITRICHINEA. THE CALLITRICHE 
FAMILY. 
Aquatic, floating herbs, with opposite or whorled leaves, and 
minute unisexual flowers in their axils. No perianth. Ovary 
and fruit either l-seeded or 4-lobed, with 1 seed in each lobe. 
Two genera, each of a single species. Allied in many respects to 
Haloragee, they are sometimes placed next to or amongst them; but 
there is no perianth, and they are therefore more frequently enumerated 
amongst anomalous Monochlamyde. [These genera are regarded by 
others as forming two families, of which Callitrichinew have been re- 
ferred both to Euphorbicee and to Haloragee. The position of Cerato- 
phyllum is quite uncertain. ] 
I. CERATOPHYLLUM. HORNWORT. 
Leaves whorled and dissected. Stamens several. Style 1. Ovary 
and fruit entire, with a single seed. 
1. C.demersum, Linn. (fig. 901). Hornwort.—A glabrous perennial, 
the stems floating like those of a Myriophyllum, and the leaves are 
whorled in the same manner, but instead of being pinnately divided 
they are twice or thrice forked, with linear often fine and subulate seg- 
ments, usually slightly toothed on the edge. Flowers small, sessile in 
the axils of the leaves, each one surrounded by a whorl of minute bracts, 
but without any real perianth ; the males consisting of 12 to 20 sessile 
oblong anthers, the females of a small ovary with a simple style. Fruit 
an ovoid, slightly compressed nut, 2 to 3 lines long, either two sharp 
species (C. demersum proper), or with a few tubercles or prickles (C. sub- 
mersum, Linn.), either scattered over the surface or united in a slightly 
prominent wing round the edge. 
In pools, slow streams, and shallow margins of lakes, dispersed almost 
all over the globe. Not uncommon in Britain. Fl. summer, but only in 
shallow water. 
II. CALLITRICHE. CALLITRICHE. 
Leaves opposite entire. Stamens solitary. Styles 2. Ovary and fruit 
4-lobed and 4-seeded. 
1. C. aquatica, Sm. (fig. 902). Common C. or Water Starwort.—A 
glabrous, slender perennial, either floating in water or creeping and root- 
ing in wet mud, flowering young so as to appear anuual, varying in 
length according to the depth of the water. Leaves either all obovate or 
