Family 2. ALISMACEAE 
By JoHN KUNKEL SMALL, 
Annual or perennial acaulescent aquatic or marsh herbs. Jeaves basal; 
petioles elongate, sheathing at the base, the blades flat, several-ribbed, often 
with spreading or deflexed lobes. Scapes erect or floating, with simple or 
branched inflorescence. Flowers perfect or unisexual, regular, whorled, borne 
in terminal racemes or panicles. Receptacle flat, conic, convex or globose. 
Calyx of 3 persistent green sepals. Corolla white or pink, of 3 deciduous 
imbricate petals. Androecium of 6 or more stamens. Filaments distinct. 
Anthers 2-ceiled, extrorse. Gynoecium of few or many verticillate or capitate 
carpels. Ovaries 1-celled. Styles rather persistent. Ovules solitary or several 
in each cavity. Fruit a head of flat or turgid achenes. Seeds curved. 
Embryo horseshoe-shaped. 
Carpels borne in one series ; achenes verticillate. 
Style lateral; achenes minutely beaked ; anthers short; petals entire. 1. ALISMA. 
Style apical ; achenes long-beaked ; anthers elongate; petalsincised. 2. MACHAEROCARPUS. 
Carpels borne in several series; achenes capitate. 
Flowers perfect. 
Style not apical ; fruit-heads not echinate ; achenes very turgid, beak- 
3 
less or obscurely beaked, . HELIANTHIUM. 
Style apical; fruit-heads echinate ; achenes mostly flat, prominently 
eaked. 4. ECHINODORUS. 
Flowers polygamous, monoecious or dioecious, the lower flowers of the 
inflorescence perfect or pistillate, the upper ones staminate. 
Lower flowers of the inflorescence perfect. 5. LOPHOTOCARPUS. 
Lower flowers of the inflorescence pistillate. 6. SAGITTARIA. 
1. ALISMA L. Sp. Pl. 342. 1753. 
Annual, or mostly perennial scapose herbs. Leaves erect or floating ; blades several- 
veined, without basal lobes, but sometimes cordate, gradually or abruptly narrowed into 
petioles. Flowers perfect, in compound often diffuse panicles. Sepals 3, broad, usually 
ribbed, persistent. Petals 3, white or pinkish, spreading, entire, deciduous. Stamens 6, 
two opposite each petal; filaments slender; anthers short. Carpels few or many, in one 
whorl, attached to the depressed receptacle by their minute bases. Achenes in 1 depressed, 
discoid whorl, ribbed or grooved on the back. 
Type species, Alisma Plantago-aquatica I. 
Achenes longer than wide, grooved on the back, the inner edges not meeting in the whorl ; 
peduncles and pedicels straight, ascending. 
Petals slightly longer than the sepals; corolla 3-4.5 mm. wide; achenes 
1.5-2 mm. long. 1. A. subcordatum, 
Petals much longer than the sepals; corolla 10-13 mm. wide ; achenes 2.5-3 
mm. lon 2. A, brevipes. 
Achenes eas long, ridged on the back, the inner edges meeting in the . 
whormpeduncles and pedicels recurved, 3. A. Geyeri. 
1. Alisma subcordatum Raf. Med. Repos. II. 5: 362. 1808. 
Alisma triviale Pursh, Fl. Am. Sept. 252. 1814. 
Alisma parviflorum Pursh, Fl. Am. Sept. 253. 1814. 
Alisma Planiago Bigel. Fl. Bost. 87. 1814. Not A. Plantagol. 1759. 
Alisma Planiago parviflorum Torr. Fl. U. S. 382. 1824. 
Alisma Plantago americanum R. & S. Syst. Veg.'7: 1598. 1830. ; 
Alisma Plantago-agquaiica Britt. & Brown, Ill. Fl. 1:85. 1896. Not A. Plantago-aquatica L. 1753. 
Plants erect, glabrous or nearly so; leaf-blades oblong, elliptic, oval or ovate, or some- 
times narrower, 3-15 cm. long, usually abruptly pointed at the apex, cuneate to truncate 
or cordate at the base; the petioles often longer than the blades; scapes 1-10 dm. tall, 
solitary or several together; the branches and pedicels in whorls of 3-10, variable in 
VoLumeE 17, Part 1, 1909] 43 
