408 ALISMACEJE. (WATER-PLANTAIN FAMILY.) 



I. A. Plantngo, L., var. Aiiicnk'aiiiim. Leaves long-petioled, 

 ovate, oblong, or lanceolate, pointed, mostly rounded or heart-shaped at the 

 base, 3-9-ncrved; panicle loose, compound, many-flowered (l-2 long); 

 carpels 15-20, obliquely obovate, forming an obtusely triangular whorl in 

 fruit. 1|. (A. trivialis and parviflora, Pursh.) Ditches and marshy places; 

 common. July, Aug. (Eu.) 



4. ECHINODORUS, Richard, Engelmann. 



Flowers perfect. Petals imbricated in the bud. Stamens 6-21 or more. 

 Ovaries several or many, imbricated in a head, forming ribbed achenia in fruit, 

 often beaked with a projecting persistent style. Habit intermediate between 

 the preceding genus and the following. (Name from e^trcoS^sr, prickly, or from 

 e'xivos, and dopos, a leathern bottle, applied to the ovary, which is in most species 

 armed with the persistent style, so as to form a sort of prickly head of fruit.) 



For the elaboration of this and the next genus I am indebted to DR. ENGEL- 



MANN. 



1. E. parvillUS, Engelm. Leaves lanceolate or spatulate, acute (J'-l' 

 long, including the petiole) ; shoots often creeping and proliferous; scapes (!'- 

 3' high) bearing a 2 - 8-flowered umbel; pedicels reflexed in fruit: stamens 9; 

 styles much shorter than the ovary ; o.chenia bf.akless, many-ribbed. Margin of 

 shallow ponds, Michigan to Illinois and westward. Flower 3" broad. 



2. E. rostra t US, Engelm. Leaves broadly heart-shaped, obtuse, nerved 

 (l'-3' long, excluding the petiole) ; scape erect, longer than the leaves, bearing 

 a branched panicle of proliferous umbels; stamens 12; styles longer than the 

 ovary : achenia beaked, many-ribbed, (i) (Alisma rostrata, Nutt.) Low river- 

 bottoms, Illinois and southward. Plant from 3' to 2 high. Flower 5" wide. 

 Head of fruit ovoid, 3'' wide. 



3. E. raclicailS, Engelm. Leaves somewhat truncately broadly heart- 

 shaped, obtuse, nerved (3' -8' broad and long, long-pctioled) ; stems or scapes 

 prostrate, creeping (2 -4 long), proliferous, bearing many whorls of flowers; 

 stamens about 21; styles shorter than the ovary; achenia short-beaked, ribbed, the 

 keeled back denticulate. TJ. (Alisma radicans, Nutt.) Swamps, W. Illinois 

 and southward. Flowers about 1' in diameter. 



5. SAGITTARIA, L. ARROW-HEAD. 



Flowers monoecious, or often dioecious in No. 2. Petals imbricated in the 

 bud. Stamens indefinite, rarely few. Ovaries many, crowded in a spherical 

 head on a globular receptacle, in fruit forming flat membranaceous winged 

 achenia. Marsh or aquatic, chiefly perennial herbs, with milky juice and fibrous 

 roots ; the scapes sheathed at the base by the bases of the long cellular petioles, 

 of which the primary ones, and sometimes all of them, are flattened, nerved, 

 and destitute of any proper blade : when present the blade is arrow-shaped or 

 lanceolate, nerved and with cross veinlets as in Alisma. Flowers (produced all 

 summer) mostly whorled in threes, with membranous bracts ; the sterile above. 

 (Name from sagitta, an arrow, from the prevalent form of the leaves.) 



