448 ALISMACEwE. ( WATER-PLANTAIN FAMILY.) 



short. Achenium 1 -seeded, 2- 3-keeled on the back. Roots fibrous. Leaves 

 mostly oval or cordate, nerved, shorter than the scape. Flowers white. 



1. A. PlantagO, L. Leaves long-petioled, ovate or oblong, acute, rounded 

 or cordate at the base, 3 - 9-nerved ; panicle large, lax, the whorled branches and 

 elongated filiform pedicels bracted at the base; achenia obtuse, 15-20 in a 

 whorl. (A. trivialis, and A. parviflora, Pursh.) Ditches and margins of ponds 

 in the upper districts, Georgia, and northward. July and Aug. Leaves 2'- 4' 

 long. Panicle 1 - 2 long. 



3. ECHINODOBUS, Richard. 



Flowers perfect, mostly in whorled racemes. Sepals 3. Petals 3, imbricated 

 in the bud, withering. Stamens few or numerous. Ovaries few or many, im- 

 bricated, forming ribbed achenia in fruit, usually beaked with the persistent 

 style. Herbs, with petioled nerved leaves. Heads mostly bur-like. 



1. E. parvulus, Engelm. Small; leaves lanceolate or spatulate, mostly 

 acute, finely nerved and somewhat pinnately-veined, commonly shorter than the 

 single or clustered 1 - 6-flowered scapes ; flowers mostly clustered or umbelled, 

 on long bracted pedicels which are recurved in fruit, stamens 9 ; achenia few, 

 shorter than the ovate sepals, obovate, flattened at the sides, and surrounded 

 with 5 prominent ribs, beakless. Margins of shallow ponds, Middle Florida, 

 and westward. July and Aug. Scapes l'-4' high. Achenia black and 

 shining. 



2. E. rostratus, Engelm. Leaves varying from lanceolate to ovate, acute 

 attach end, or rounded or cordate at the base, 5-nerved, about as long as the 

 petiole ; scape rigid, erect, longer than the leaves ; whorls few ; pedicels erect or 

 spreading ; sepals ovate, many-nerved, shorter than the oval bur-like head ; sta- 

 mens 12 ; style longer than the ovary; achenia numerous, strongly 3-ribbed on 

 the back, with fainter lateral and intermediate ribs, beaked with the long persist- 

 ent style. South Florida, and westward. Scape simple, 3'- 8' high, or oc- 

 casionally 2 high and paniculately branched. Leaves 1' -2' long. Flowers 5" 

 wide. 



3. E. radicans, Engelm. Leaves large, long-petioled, ovate, cordate or 

 truncate at the base, obtuse, 7 - 9-ribbed ; scape elongated, prostrate, rooting and 

 proliferous; whorls several, remote; pedicels slender, spreading, or recurved; 

 stamens about 20 ; style shorter than the ovary ; heads globose, longer than the 

 many-nerved sepals ; achenia very numerous, short-beaked, ribbed and slightly 

 denticulate on the back. (Alisma radicans, Nutt.) Swamps, Florida to North 

 Carolina, and westward. July - Sept. Scape 2 - 4 long. Leaves 3' - 8' long. 

 Flowers 8" -12" wide. 



4. SAGITTARIA, L. ARROW-GRASS. 



Flowers monoecious, in a whorled raceme, the upper ones sterile. Sepals 3, 

 persistent. Petals 3, imbricated in the bud, withering. Stamens few or many. 

 Ovai-ies crowded in a globular head. Achenia flat, membranaceous, winged. 

 Marsh or aquatic herbs, with scape-like stems, and variously-shaped nerved and 



