504 HALORAGIDACEAE. (Vor. Il. 
5. Myriophyllum himile (Raf.) Morong. Low Water-Milfoil. (Fig. 2621.) 
Burshia humilis Raf. Med. Rep. (II.) 5: 361. 1808. 
Myriophyllum ambiguum Nutt. Gen. 2: 212, 1818. 
Myriophyllum humileMorong, Bull. Torr. Club, 18: 242. 1891. 
Typical form terrestrial, 1/-114’ 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 1/’ 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. F1. Bor. Am, 2: 191. 1803. 
Floral leaves in whorls of 3’s 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 
6-10 pairs, capillary; flowering spike elongated (sometimes 
18’ long); petals 4; stamens 4, rarely 6; fruit 1’” long, and 
slightly longer than thick; carpels 2-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. go. 1788. 
Myriophyllum scabratum Michx. Fl. Bor. Am, 2: 190. 1803. 
Myriophyllum pinnatum B.S.P. Prel. Cat. N. Y.16. 1888. 
Leaves in whorls of 3’s—5’s, or sometimes scattered, 
the floral ones linear, serrate or pectinate, 214’/-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 1’’ long and somewhat more than 4’ 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 
in the axils; petals 4, purplish, oblong; pistillate flow- 
ers only seen; styles 4, short; stamens 4, minute, 
abortive; fruit about 1/’ long and %” thick; carpels We - 
crossed longitudinally by 3-4 rough tuberculate or ee Se HER 
. . back ly =< 
slightly toothed ridges, 2 on the back and commonly \\ NW 
2 q iws ie 
I on each margin; groove between the carpels shallow. i es 
In still water, Maine to Michigan. = 
