230 



montaiia which are monoecious. By some good judges, Calli- 

 tricJie has been included among the EtiphorbiacecB, 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. 



I. 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. MyriopJiyllum. 



I. Hippuris. L. Gen. PI. n. i. (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 more in a whorl. 



I . H . vulgaris. 



