ALISMACEAE 41 



tary, erect. Carpels leathery, 3-6, distinct or partially united until fully mature, each 

 opening by a ventral suture. Seeds solitary, erect, flattened or angled. 



1. Triglochin striata K. & P. Foliage'' glabrous. Leaves basal ; blades slightly 

 fleshy, linear, attenuate, 0.5-2 mm. broad, 2-3 dm. long, erect : scapes erect, solitary or 



2 together, angled, about as long as the leaves or longer : racemes 2-15 cm. long, barely if 

 at all interrupted : pedicels 1-1.5 mm. long, not crowded : perianth greenish or light yel- 

 low : sepals 3, oval or ovate, obtuse, less than 1 mm. long : stigmas plumose : fruit sub- 



Slobose, 1.5-2 mm. in diameter, somewhat 3-winged at maturity : carpels 3, 3-ribbed on 

 le back. [Triglochin triandra Michx.] 



In salt marshes, Maryland to Florida and Louisiana. Summer and fall. ARROW-GRASS. 



FAMILY 2. ALISMACEAE DC. WATER-PLANTAIN FAMILY. 



Annual or perennial acaulescent aquatic or marsh herbs. Leaves basal : 

 petioles elongated, sheathing at the base : blades flat, several-ribbed, often with 

 spreading or deflexed lobes. Scapes erect or floating, mostly simple to the in- 

 florescence. Flowers perfect, monoecious or dioecious, regular, whorled, dis- 

 posed in terminal racemes or panicles. Receptacle flat or globose. Calyx of 



3 persistent sepals. Corolla white or pink, of 3 deciduous imbricated petals. 

 Androecium of 6 or more stamens. Filaments distinct. Anthers 2-celled, 

 extrorse. Gynoecium of few or many carpels. Ovaries 1-celled. Styles rather 

 persistent. Ovules solitary in each cavity. Fruit a head of flattened achenes. 

 Seeds curved. Embryo horseshoe-shaped 



Carpels in a ring on a flat receptacle. 1. ALISMA. 

 Carpels curved in many series on a convex or globose receptacle. 

 Flowers perfect or polygamous. 



Sepals spreading : pedicels not recurved at maturity. 2. ECHINODORUS. 



Sepals appressed : pedicels recurved at maturity. 3. LOPHOTOCARPUS. 



Flowers monoecious or dioecious. 4. SAGITTARIA. 



1. ALISMA L. 



Annual, or mostly perennial scapose herbs. Leaves erect or floating : blades several- 

 ribbed, without basal lobes, narrowed into petioles. Flowers perfect, in compound or 

 umbel-like panicles. Stamens 6-9, rather perigynous : filaments slender. Carpels few or 

 many, in one whorl on a flat receptacle. Achenes in 1 whorl, 2-3-ribbed on the back, 

 1-2-ribbed on the sides. WATER PLANTAIN. 



1. Alisma subcordatum Eaf. Perennial, glabrous or nearly so. Leaf-blades ob- 

 long, elliptic, oval or ovate, or sometimes narrower, 3-15 cm. long, usually abruptly 

 pointed, entire, cuneate to truncate, or cordate at the base ; petioles often longer than the 

 blades : scapes 1-10 dm. tall, solitary or several together ; branches and pedicels in whorls 

 of 3-10, variable in length : bracts lanceolate or linear, often acuminate : sepals broadly 

 ovate to suborbicular, obtuse : petals white or pinkish, 1-2 mm. long : mature heads 4-6 

 mm. broad, flat : achenes obliquely obovate, 2 mm. long ; beak small, ascending. 



In swamps and shallow water. Nova Scotia to North Dakota, Florida and Texas. Spring to fall. 



2. ECHINODORUS L. C. Kich. 



Annual or perennial usually acaulescent marsh herbs. Leaves erect or ascending: 

 blades sometimes ample, several-ribbed. Scapes usually surpassing the leaves. Flowers 

 perfect, in whorls disposed in racemes or panicles. Stamens 12-30 : filaments often about 

 as long as the anthers. Carpels numerous, inserted on a convex or globose receptacle. 

 Style obliquely apical : stigma simple. Achenes forming a bristly head, leathery, ribbed, 

 and beaked by the persistent style. 



Carpels few, usually less than 14 maturing : flowers in terminal umbel-like clusters. 1. E. parvulus. 

 Carpels numerous, many maturing : flowers in terminal panicles, the main axis of 



the panicle sometimes greatly elongated. 

 Scapes creeping near the base : style shorter than the ovary : beak about % as long 



as body of the achene. 2. E. radicans. 



Scapes erect or ascending : style longer than the ovary : beak fully % as long as 



body of the achene. 3. E. cordifolius. 



1. Echinodorus parvulus Engelm. Leaf-blades linear to linear-elliptic, 1-3 cm. 

 long, acute at both ends, longer than the petioles or much shorter : scapes solitary or 

 several together, surpassing the leaves or overtopped by them, topped by a whorl of 2-8 

 pedicels, these spreading or curved, 5-25 mm. long, unequal in length : bracts white, 



