504 



HALORAGIDACEAE. 



[VOL. II. 



Myriophyllum humile (Raf.) Morong. Low Water-Milfoil. (Fig. 2621.) 



Burshia humilis Raf. Med. Rep. (II.) $: 361. 1808. 

 Myriophyllum ambiguum Nutt. Gen. 2: 212. 1818. 

 Myriophyllum humile Morong:, Bull. Torr. Club, 18: 242. 1891. 



Typical form terrestrial, I'-iJ^' high, rooting in mud 

 on shores. Leaves linear, entire or pectinate. Floating 

 forms with stems often 12' long, branched, with all or 

 most of the leaves pectinate into capillary segments; 

 these produce the typical form if they take root; petals 

 4, purplish; stamens 4; fruit usually less than \" long 

 and about as thick at base, its carpels smooth, or rarely 

 slightly roughened, separated by a shallow groove. 



In ponds, Massachusetts and Rhode Island to Maryland and 

 Illinois. Variable in appearance, but the variations are 

 manifestly only conditions of the plant dependent upon its 

 environment. 



6. Myriophyllum heterophyllum Michx. Vari- 

 ous-leaved Water-Milfoil. (Fig. 2622.) 



Myriophyllum heterophyllum Michx. Fl. Bor. Am. 2: 191. 1803. 

 Floral leaves in whorls of 3*8 to 5's, linear, ovate or 

 lanceolate, serrate or rarely entire, much longer than the 

 flowers. Submerged leaves subverticillate or scattered, 

 crowded, pectinate-pinnatifid, about 10" long, the divisions 

 6-ro pairs, capillary; flowering spike elongated (sometimes 

 18' long); petals 4; stamens 4, rarely 6; fruit i" long, and 

 slightly longer than thick; carpels a-keeled on the back, 

 usually slightly scabrous. 



In ponds, Ontario and New York to Florida, west to Minnesota, 

 Texas and Mexico. 



7. Myriophyllum pinnatum (Walt.) B.S.P. 

 Pinnate Water-Milfoil. (Fig. 2623.) 



Potamogeton pinnatum Walt. Fl. Car. 90. 1788. 

 Mvriophyllum scabratum Michx. Fl. Bor. Am. a: 190. 1803. 

 .l/i ; -iitphyllum pinnatum H.S.P. 1'rel. Cat. N. Y. 16. 1888. 



Leaves in whorls of 3's-5's, or sometimes scattered, 

 the floral ones linear, serrate or pectinate, 2# // -6 / ' 

 long, gradually passing into the submerged ones which 

 are crowded, pinnately dissected, the divisions few and 

 capillary; spikes 4 / -8' long; petals purplish; stamens 

 4, very rarely 6; carpels strongly 2- keeled and sca- 

 brous on the back, separated by deep grooves; mature 

 fruit about i" long and somewhat more than ft" thick. 



In ponds, Rhode Island to Florida, west to Missouri, 

 Louisiana, Texas, and south to Panama. 



8. Myriophyllum Farwellii Morong. Far- 

 well's Water-Milfoil. (Fig. 2624.) 



M. Farwellii Morong, Bull. Torr. Club, 18: 146. 1891. 



Dioecious (?) Specimens with submerged leaves 

 only, in whorls of 3's-6's, or scattered, narrow, pin- 

 nately parted, the divisions finely capillary in 5-7 op- 

 posite or subopposite pairs, with minute black spines 

 iu the axils; petals 4, purplish, oblong; pistillate flow- 

 ers only seen; styles 4, short; stamens 4, minute, 

 abortive; fruit about \" long and ft" thick; carpels 

 crossed longitudinally by 3-4 rough tuberculate or 

 slightly toothed ridges, 2 on the back and commonly 

 i on each margin ; groove between the carpels shallow. 



In still water, Maine to Michigan. 





