502 



HALORAGIDACEAE. 



[VOL. II. 



Etnersed leaves linear-lanceolate to oblong, serrate; fruit sharply angled. 

 Leaves all pectinate-pinnatifid; fruit obtusely angled. 



1. P. palustris. 



2. P. pectinata. 



i. Proserpinaca palustris L,. Mermaid-weed. (Fig. 2615.) 



Proserpinaca palustris L. Sp. PI. 88. 1753. 



Glabrous, simple or sometimes branched, 

 8 / -2O / high. Emersed 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 seg- 

 ments 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 Lake Huron, 

 south to Florida. Iowa and Central America. 

 Also in Cuba. July. 



2. Proserpinaca pectinata Lam. Cut-leaved 

 Mermaid- weed. (Fig. 2616.) 



Proserpinaca pectinata Lam. Tabl. Rncycl. pl.$o. f.i. i: 214. 



'79i- 

 Proserpinaca pectinacea T. & G. Fl. 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 \W long by i" thick, 

 the faces flat or slightly convex, often wrinkled or some- 

 what tuberculate, the angles obtuse. 



In sandy swamps near the coast, eastern Massachusetts to 

 Florida, west to Louisiana. Summer. 



3. MYRIOPHYLLUM L. Sp. PI. 992. 1753. 



Aquatic herbs, with verticillate or alternate leaves, the emersed ones entire, dentate or 

 pectinate, the submerged ones pinnatifid into capillary segments, and axillary commonly 

 monoecious 2-bracted flowers, often interruptedly spicatc. Upper flowers generally staminate 

 with a very short calyx-tube, its limb 2-4-lobed, or none; petals 2-4; stamens 4-8. Intermedi- 

 ate flowers often perfect. Lower flowers pistillate, the calyx more or less deeply 4-grooved 

 and with 4 minute lobes, or none; ovary 2-4-celled; ovule i in each cavity, pendulous; 

 styles 4, short, often plumose. Fruit splitting at maturity into 4 bony i -seeded indehiscent 

 carpels which are smooth, angled or tuberculate on the back. [Greek, myriad-leaved.] 



About 20 species, of wide geographic distribution. In addition to the following, another occurs 

 in the western United States. The plants flower in summer. 



Carpels smooth. 



Flowers in emersed spikes. 



Floral leaves shorter than the flowers. 

 Flowers in whorls. 



Flowers alternate, or the lower sub-verticillate. 

 Floral leaves longer than the flowers, pinnatifid. 

 Floral leaves reduced to minute bracts. 

 Flowers on both emersed and submersed stems. 

 Flowers only on submersed stems. 

 Carpels rough or tuberculate. 

 Flowers on emersed spikes. 



Floral leaves ovate or lanceolate, serrate. 

 Floral leaves linear, pectinate. 

 Flowers on submersed stems. 



i. M. spicatum. 



3. M. alterniflorum. 

 2. M. vertictllalum. 



4. M. tenellum. 



5. M. humile. 



9. M. proserpinacoid.es. 



6. M. heterophyllum. 

 j. M. pinnatum. 

 8. M. Faru'ellii. 



