ALISMACEAE 43 



1. TRIGLOCHIN L. 



Acaulescent herbs, the perianth inconspicuous. ARROW-GRASS. 



1. Triglochin striata E. & P. Plant glabrous: leaves 2-3 dm. long, attenuate: 

 racemes 2-1.5 cm. long: sepals ovate or oval, less than 1 mm. long, greenish or light 

 yellow: fruit 1.5-2 mm. in diameter, each carpel 3-ribbed. 



In salt marshes, Maryland to Florida and Louisiana. Also in California, Mexico and 

 South America. Summer and fall. 



FAMILY 2. ALISMACEAE DC. WATER-PLANTAIN FAMILY. 



Annual or perennial herbs. Leaves basal, the blade flat, often with basal 

 lobes, or mere phyllodia. Flowers perfect, monoecious or dioecious, whorled. 

 Sepals herbaceous. Petals tender, white or pink. Gynoecium of few to many 

 carpels. Style manifest. Fruit a head of flattened or turgid achenes. 



Carpels borne in 1 series: achenes verticillate. 1. ALISMA. 



Carpels borne in several series: achenes capitate. 

 Flowers perfect. 



Style not apical: fruit-heads not echinate: achenes turgid, beakless 



or obscurely beaked. 2. HELIANTHIUM. 



Style apical: fruit-heads echinate: achenes flat, prominently beaked. 3. 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. 4. LOPHOTO CARPUS. 



Lower flowers of the inflorescence pistillate. 5. SAGITTARIA. 



i. ALSMA L. 



Leaves without basal lobes. Flowers perfect, in compound panicles. Stamens 

 mostly 6. Achenes in 1 whorl. WATER PLANTAIN. 



1. Alisma subcordatum Raf. Leaf -blades entire, 3-15 cm. long, long-petioled : 

 scape 1-10 dm. tall, the branches, or pedicels, whorled in 3's or 10 J s: sepals obtuse: 

 petals 1-2 mm. long: fuit-heads depressed, 3.5-4.5 mm. wide: achenes 1.5-2 mm. 

 long. 



In swamps or shallow water, Massachusetts to Minnesota, Florida and Texas. Spring 

 to fall. , 



2. HELIANTHIUM Engelm. 



Leaves without basal lobes, the blades narrow. Flowers perfect, borne in 

 racemes. Stamens 6 or 9. Achenes borne in an inconspicuous naked head. 



1. Helianthium parvulum (Engelm.) Small. Leaf -blades linear or linear- 

 elliptic, 1-3 cm. long: scape 3-11 cm. tall, with a terminal whorl of 2-8 flowers: 

 petals 1.5-2 mm. long: fruit -heads 3-4 mm. thick: achenes barely 1 mm. long. 

 [Echinodorus parvulus Engelm.] 



In mud, Massachusetts to Ontario, Minnesota, Florida and Texas. Also in tropical 

 America. Spring to fall. 



3. ECHINODORUS L. C. Rich. 



Leaves with rounded basal lobes. Flowers perfect, in racemes or panicles. 

 Stamens 12-30. Achenes borne in a bristly naked head. BUR-HEAD. 



Flowers, and fruit-heads, borne on pliable curved pedicels: style shorter than the ovary: achene- 

 ' beak about % as long as the body. " 1. E. radicans. 



Flowers, and fruit-heads, borne on stiff spreading pedicels: style longer than the 



ovary: achene-beak fully X as long as the body. 2. E. cordifolius. 



1. Echinodorus radicans (Nutt.) Engelm. Stems creeping near the base: leaf- 

 blades ovate or oblong, 5-20 cm. long: scapes often creeping, the flower-whorls 

 remote: petals about 6 mm. long: fruit-heads 7-8 mm. thick: achenes 2 mm. long, 

 short-beaked. 



In ponds and swamps, Illinois to Kansas, District of Columbia, Florida, California and 

 Mexico. Spring and summer. 



2. Ecbinodorus cordifolius (L.) Griseb. Stems erect or ascending: leaf -blades 

 lanceolate to broadly ovate, 4-20 cm. long: scapes 1-5 dm. tall, the flower-whorls less 

 remote than in E. radicans: petals 4-6 mm. long: fruit-heads 4-6 mm. thick: achenes 

 2.5-3 mm. long, long-beaked. 



In swamps and ditches, Illinois to Kansas, Florida, Texas, Mexico and Central America. 

 Also in the West Indies. Spring and summer. 



4. LOPHOTOCARFUS T. Durand. 



Leaves often with basal lobes, but variable. Flowers monoecious, the upper 

 ones staminate. Stamens 9-15. Achenes in a head embraced by the calyx. 



