230 
montana which are monoecious. By some good judges, Cal/i- 
triche has been included among the Luphorbiacee, with which, 
indeed, it has affinities, -but from which it is widely divergent in 
having two styles and four-celled, indehiscent fruit, as well as in 
other characters. ‘ : 
The species as found in our country are, as a rule, strictly 
aquatic, but not invariably so, as a few of them grow on mud or 
moist ground by the side of streams or ponds, and two species of 
Callitriche make their home under the shade of houses or in the 
woods. 
About thirty species are found in Canada and the United 
States. 
The genera agree in having pendulous, anatropous ovules, 
nut-like or drupaceous, indehiscent, angular, costate or winged 
seeds, and a fleshy albumen with the embryo in its axis. 
They may be briefly distinguished as follows: 
Stamens one. 
Ovary one-celled. Leaves verticillate, linear or obovate. 
1. Hippuris. 
Ovary four-celled. Leaves opposite, linear or spatulate. 
2. Callitriche, 
Stamens two to eight. 
Fruit triangular. Leaves alternate, pectinate or pectinate- 
pinnatifid. 3. Proserpinaca. 
Fruit four-sided. Leaves verticillate, subverticillate or scat- 
tered. The emersed entire, toothed or pectinate, the sub- 
merged pinnatifid. 4. Myriophyllum. 
1. Hippuris. L. Gen. Pl. n. 1. (1737). 
Flowers small, axillary, perfect, or by abortion sometimes 
neutral or pistillate. Apetalous. Calyx tube adherent to the ovary, 
the limb minute, entire. Stamens one, in the perfect flowers 
inserted on the margin of the calyx. Style filiform, stigmatic its 
whole length, and lying in a groove of the anther. Drupe one- 
celled, one-seeded. Only three species are known, all occurring 
in North America 
Leaves linear, acute, six to twelve or morein a whorl. 
1. H. vulgaris. 
