Genus 



WATER MILFOIL FAMILY. 



2. Hippuris tetraphylla L. f. Four-leaved Mare's-tail. 

 Fig. 3078. 



Hippuris tetraphylla L. f. Suppi. 81. 1781. 



Hippuris maritima Hell. Dissert. Hippur. pi. i. 1786. 



Smaller than the preceding species. Stem 4'-is' high;, leaves 



obovate or oblanceolate, entire, in verticils of 4-6, not sphacelate 



at the apex or but slightly so, 4"-y" long. 



Labrador and Quebec to Hudson Bay and Alaska. Also in north- 

 ern Europe and Asia. Summer. 



2. PROSERPINACA L. Sp. PL 88. 1753. 



Aquatic herbs, with simple stems decumbent at the base. 

 Leaves alternate, very various, dentate or pectinate-pinnatifid. 

 Flowers perfect. Tube of the calyx adnate to the triquetrous 

 ovary, the limb 3-4-parted. Petals none. Stamens 3-4. Styles 

 3-4, cylindric or conic-subulate stigniatic above the middle. Fruit bony, 3-4-angled, 3-4-celled, 

 with I seed in each cavity. [Middle Latin, forward-creeping.] 



Three or four species, natives of eastern North America, extending to the West Indies and 

 Guatemala. Type species ; Proserpinaca palustris L. 



Emersed leaves linear-lanceolate to oblong, serrate; fruit sharply angled. i. P palustris. 



Leaves all pectinate-pinnatifid ; fruit obtusely angled. 2. p pectinata. 



I. Proserpinaca palustris L. Mermaid- 

 weed. Fig. 3079. 



Proserpinaca palustris L. Sp. PI. 88 1753. 



Glabrous, simple or sometimes branched, 

 8'-2o' high. Em'Crsed leaves oblong or linear- 

 lanceolate, io"-2' long, I "-6" wide, sharply 

 serrate, the submerged ones pectinate or pec- 

 tinate-pinnatifid into stiff linear acute segments 

 which are often serrulate, bearing a minute 

 black spine in their axils ; flowers solitary or 

 several together, sessile in the axils of the 

 emersed leaves ; fruit about 2" long and 2" 

 thick, sharply 3-angled, the faces concave, 

 smooth or rugose. 



In swamps, New Brunswick to Minnesota, Flor- 

 ida, Iowa, Texas and Central America. Alsc in 

 Bermuda. July. 



2. Proserpinaca pectinata Lam. Cut-leaved Mer- 

 maid-weed. Fig. 3080. 



Proserpinaca pectinata Lam. Tab!. Encycl. pi. 50. f.i.i: 214. 



1791- 

 Proserpinaca pectinacea T. & G. FI. N A. i : 528. 1840. 



Resembling the preceding species, but usually smaller. 

 Leaves all pectinate or pinnatifid, the segments shorter and 

 rarely serrulate, more subulate, or capillary ; calyx-lobes 

 broader; fruit smaller, about li" long by i" thick, the 

 faces flat or slightly convex, often wrinkled or somewhat 

 tuberculate, the angles obtuse. 



In sandy swamps near the coast, Maine to Florida, west to 

 Louisiana. Summer. 



Proserpinaca intermedia Mackenzie, from swamps in south- 

 ern New Jersey and Georgia, is quite intermediate between the 

 two above species and may be a hybrid between them. 



