244 



all pinnatifid with hair-like divisions, subverticillate or scattered. 

 It rarely flowers or fruits, and when it does the inflorescence may 

 be seen scattered here and there in the axils of the leaves. One 

 or more of the forms occur from eastern Massachusetts to Mary- 

 land and Tennessee, and west to Illinois and Indiana. 



6. M. proserpinacoides. Gill, in Hook. Bot. Misc. 3, 313 (1833). 



This is a South American species introduced from Chili or 

 Buenos Aires, where it is a native. It has partially naturalized 

 itself in Hopkins' pond, near Haddonfield, and other places in 

 New Jersey, and seems to be spreading. All the plants occurring 

 in our waters appear to have sprung from stock imported several 

 years ago by the florist, Mr. E. D. Sturtevant, of Bordentown, 

 New Jersey, who writes that " it is entirely hardy here, below 

 the reach of ice or frost." 



Hooker describes it as monoecious and dioecious. I have 

 seen only pistillate plants. These are very vigorous, 10 to 40 

 cm. high, even lifting themselves out of the water and growing 

 quite as well above as below it. Normally, however, it seems to 

 be a submerged plant. Leaves all alike, smooth, glaucous, pectin- 

 ate-pinnatifid, in crowded verticils of fives, 15 to 20 mm. long, 

 pinnae linear, twenty to twenty-five in number, the pairs opposite 

 or subopposite, each segment about 5 mm. long, and sharply 

 pointed. Stamens said by Gillies to be eight. Pistillate flowers 

 axillary, about i mm. high, without petals, with four white plu- 

 mose stigmas. Fruit not seen, but as indicated by the ovaries, 

 the carpels should be smooth. Between the bases of the leaves 

 and among the flowers are many small white trichomes, or hair- 

 like bracts. 



7. M. heterophyllum. Michx. Fl. 2, 191 (1803). 



Potamogeton verticillatum. Walt. Fl. Car. 90 (1788). 



Floral leaves in whorls of threes and fives, linear, ovate or 

 lanceolate, serrate or rarely entire, much longer than the flowers, 

 sometimes as much as 18 mm. in length and 4 mm. broad ; sub- 

 merged leaves verticillate or subverticillate, crowded, about 2 cm. 

 long, with six to ten pairs of capillary pinnae. The flowering 

 spike occasionally attains the length of 40 or 50 cm. Petals 

 somewhat persistent. Stamens four, very rarely six. Fruit 2 



