678 ALISMACE^ ALISMA 



with a very hard coat. In cold bogs, California to Alaska and across the 

 continent : also in Europe and Asia. 



ORDER CVI ALISMACE^ DC. Fl. France iii, 181. 



Marsh herbs with scape-like stems, broad leaves with sheath- 

 ing base and conspicuous perfect or unisexual flowers in pani- 

 cles or racemes. Perianth of 3 herbaceous persistent sepals and 

 as many often conspicuous white deciduous sepals. Stamens 

 6 or more, included. Ovaries numerous, distinct, 1-celled and 

 mostly 1-ovuled, becoming achenes in fruit. Seed erect, campy- 

 lotropous, with membranous testa and no albumen. Embryo 

 strongly recurved or uncinate. 



1 Alisma Flowers perfect : stamens usually 6 : carpels numerous, ver- 



ticillate, distinct, obovate-oblong. 



2 Sagittaria Powers monoecious or direcious: carpels numerous, flat- 



tened and membranously winged. 



1 ALISMA L. Sp. 342. 



Perennial herbs growing in shallow water or mud with broad 

 leaves and small flowers in a verticillately branched panicle. 

 Flowers perfect, small, numerous, on unequal 3-bracteolate pedi- 

 cels. Stamens 5, rarely more, with short filaments, Ovaries 

 distinct, numerous, borne in several whorls on a small flat re- 

 ceptacle, 1-ovuled. Styles very short, ventral. Achenes in a 

 crowded whorl, ovate-oblong, flattened. 



A. Plant ago -aquatica L. Sp. 342. Scapes >-3 feet high, usually 

 solitary: leaves ovate, acute at the apex, cordate, rounded or narrowed at 

 base, or when floating sometimes lanceolate or even linear, on petioles 1-10 

 inches long : inflorescence a large loose panicle 5-15 inches long : pedicels 

 verticillate in 3's-lO's, subtended by 3 striate acuminate bracts : petals 3^-1 

 line long: styles deciduous, the base remaining as a small point or short 

 beak on the inner curve of the achenes : stigmas small, terminal : achenes 

 nearly 1 line long, arranged in a circle forming an obtusely triangular 

 truncate head. In shallow water or mud, throughout North America: 

 also in Europe and Asia. 



2 SAGITTARIA L. Sp. 993. 



Perennial aquatic or bog herbs with broadly sheathing leaves, 

 often without blades, and mostly simple stems bearing one to few 

 whorls of flowers mostly in threes. Flowers monoecious or some- 

 times dioecious, the staminate ones above. Petals usually con- 

 spicuous. Stamens usually numerous, inserted on the convex 

 receptacle: anthers 2-celled, dehiscent by lateral slits. Pistillate 

 flowers with numerous distinct ovaries. Stigmas small. Achenes 

 numerous, densely aggregated in subglobose heads. 



S. arifolia Nutt. J. G. Smith Ann. Rep. Mo. Bot, Garden vii, 32. 



