112 HALORAGACEiE. 



the lower part usually submerged. Flowers mostly solitary, sometimes 2 — 4 

 together, very small, nearly sessQe. Stigmas purplish. 



Common Mermaid Weed. 



2. P. pedinacea Lam. : leaves all pinnatifid-pectinate ; fruit large, an- 

 gular, obtuse. P. palustris var. /? Mich. 



Sandy swamps. Mass. to Flor. Apg. %. — Distinguished from the former, 

 by having the leaves all finely pectinate and the fruit with rather obtuse in- 

 stead of acute angles. Pectinate Mermaid Weed. 



2. MYRIOPHYLLUM. I/wm.— Water Milfoil. 



(From the Greek fivpios, myriad, and cprvWov, a leaf; in allusion to the minute 

 divisions of the leaf) 



Flowers moncecious or rarely perfect. Sterile Fl. Calyx 



4-parted. Petals 4, ovate, sometimes inconspicuous or 



wanting. Stamens 4 — 8. Perfect Fl. Calyx adhering to 



the ovary ; limb 4-lobed. Petals none. Nuts 4, compressed 



or subglobose, 1 -seeded. 



* Flowers octandrous. 



1. M. spicatum Linn.: leaves verticillate, pinnately divided, segments 

 capillary ; floral leaves shorter than the flowers ; lower subserrate and 

 mostly very entire; petals broad-ovate; carpels smooth and even. 



In water. Can. aaid N. S. Aug., Sept. %.—Stem slender, varying in 

 length with the depth of the water. Leaves in whorls, 3 — 5, pectinate. Flowers 

 in a terminal nearly naked spike. Spiked Water Milfoil. 



2. M. verticillaium Linn. : leaves verticillate, pinnately divided into ca- 

 pillary or setaceous segments; floral leaves pectinate-pinnatifid, usually 

 much longer than the flowers ; petals oblong-obovate ; carpels smooth and 

 even. 



In water. Can. to Flor. W. to Texas and Oregon. July — Sept. %.. — Stem 

 long and stouter than in the preceding. Flowers in a terminal leafy spike, 

 upper ones sometimes perfect. Whorled Water Milfoil. 



** Flowers tetrandrous. 



3. M. heterophyllum Mich. : leaves verticillate, pinnately divided into ca- 

 pillary segments ; floral leaves ovate or lanceolate, sharply serrate, crowded ; 

 petals oblong ; carpels minutely roughened, slightly 2-ridged on the back. 



In water. Can. to Flor. W. to Texas. July. 1].. — Stem branching, thick. 

 Floivers purple, whorled in the axils of the upper leaves. Stamens 4. (6, Mi- 

 chaux.) Various-leaved Water Milfoil. 



4. M. ambiguum NuU. : submersed leaves cut into capillary segments ; 

 the emersed ones pectinate ; floral leaves linear, tapering into a short peti- 

 ole, sparingly incised or toothed, sometimes entire ; flowers mostly perfect; 

 petals oblong ; carpels smooth and even. M. capillaceum Terr. Camp. 

 M. procuvibens Dig. 



Ponds and ditches. Mass. to Penn. July, Aug. %.^Stems 2 — 6 inches 

 long and creeping in the mud, or when floating in water, long and slender. 

 Leaves variously divided, depending upon the place of growth. Flowers small, 

 purplish. . Polymorphous Water Milfoil. 



