1. Alisma L. Water Plantain. Mud Plantain 



Aquatic herbs, perennial or sometimes behaving as annuals, emersed or grow- 

 ing on wet mud, rarely submersed, from an apically flattened corm and fibrous 

 roots; leaves basal, erect or rarely floating, with lanceolate or oblong-ovate to 

 broadly ovate blades, rarely reduced to ribbonlike phyllodes; inflorescence a large 

 open panicle; flowers small, 3-10 mm. broad, perfect, numerous, on 3-bracteate 

 pedicels unequal in length; sepals 3, green, persistent; petals 3, white or occa- 

 sionally rose or pink; stamens 6 to 9; pistils separate, arranged in a more or less 

 3-sided whorl on the receptacle; fruit an achene, with 1 or 2 grooves to almost 

 plane on the back. 



About 10 species mostly in the North Temperate Zone. 



1. Achenes about as wide as long, distinctly bisulcate on the back with the 

 median rib typically broad and rounded; pedicels stout; petioles 

 4-6 mm. wide; leaf blade elliptic-lanceolate to narrowly lanceolate, 

 to about 2.5 cm. wide 1. A. gramineum. 



1. Achenes longer than wide, with a solitary groove to almost plane on the back; 



pedicels slender; petioles less than 4 mm. wide; leaf blade typically 

 broadly elliptic and usually much more than 2.5 cm. wide (2) 



2(1). Achenes 2 mm. long or less, the dorsal groove shallow or with a somewhat 

 depressed slight thickening in the trough; fruiting heads 3.5 mm. or 



less in diameter; distribution in Oklahoma and Texas 



2. A. subcordatum. 



2. Achenes more than 2 mm. long, the dorsal groove deep; fruiting heads more 



than 3.5 mm. in diameter; distribution in New Mexico and Arizona 

 3. A. triviale. 



1. Alisma gramineum Gmel. Fig. 55. 



Submersed or amphibious perennial herb 5-20 cm. high, erect or ascending or 

 (when plant submersed) leaves and stems floating; leaves usually erect, with 

 long broad petioles (4-6 mm. wide) and linear-lanceolate to lanceolate blades 

 (these rarely absent), to about 2.5 cm. wide; inflorescence a scapose verticillate 

 panicle to 2 dm. long, sometimes shorter than the leaves; branchlets and pedicels 

 subtended by 2 or 3 lanceolate papery bracts; pedicels stout, often recurved in 

 fruit; flowers 5-7 mm. broad; sepals green, persistent; petals usually white, 

 rhombic, entire to somewhat ^erose; stamens 6 to 9; pistils in an obscurely 3-sided 

 whorl; fruiting heads 3-4 mm. in diameter; achenes often orbicular to orbicular- 

 cuneate in outline, about 2.5 mm. in diameter, the beak on the inner margin, 

 distinctly bisulcate on the back with the median rib broad and rounded. A. Geyeri 

 Torr., A. gramineum var. Geyeri (Torr.) Samuelsson. 



On mud and in shallow water of lakes in N.M. (Rio Arriba and Sandoval cos.) 

 and Ariz (Coconino Co.), June-Sept.; from Calif., Ariz, and N.M., n. to Wash, 

 and e. to Minn. 



Our material is usually referred to var. angustissimum (DC.) Hendricks. 



2. Alisma subcordatum Raf. 



Erect perennial herb with a basal cluster of erect long-petioled laminated leaves 

 surrounding a scape, essentially glabrous; leaf blades ovate to elliptic, cuneate to 

 cordate at base, abruptly acute at apex, to 12 cm. long and 8 cm. wide, usually 

 shorter than the petioles; scape to 6 dm. tall, with whorled panicled branches of 

 small white or pinkish flowers; bracts lanceolate, acuminate, about 1 cm. long; 

 pedicels filiform; flowers perfect, numerous; sepals broadly ovate to suborbicular, 

 obtuse, to 2.5 mm. long; petals to 2.5 mm. long; anthers spherical, 0.3-0.5 mm. 

 long; ovaries many in a simple circle on a small flattened receptacle; style 0.2-0.4 

 mm. long, about one fourth as long as ovaries; fruiting heads 3.5 mm. or less in 



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