diameter; achenes obliquely obovate, 1.5-2 mm. long, the solitary dorsal groove 

 shallow or with a somewhat depressed slight thickening in the trough, the minute 

 beak ascending. A. parviflorum Pursh, A. Plantago-aquatica var. parviflorum 

 (Pursh) Far\\'. 



Usually in shallow water of marshes, streams and ponds in Okla. (Delaware, 

 McCurtain, Mayes, Johnston, Murry and Craig cos.), n.e. Tex. (Bowie Co.) and 

 the Tex. Panhandle (Hemphill Co.), June-Sept.; Ont., N. E. and N. Y., w. to 

 Minn, and Neb., s. to Fla. and Tex. 



Though reported from Arizona, we have seen no material of this species from 

 the state. 



3. Alisma triviale Pursh. Fig. 55. 



Erect perennial to 12 dm. tall; leaves usually long-petioled, linear-lanceolate to 

 broadly elliptic, 5-20 cm. long, cuneate to truncate or subcordate at base, sub- 

 obtuse to abruptly acute at apex; inflorescence on an erect scape with several 

 whorls of branches, each with 1 or more whorls of flowers or further compounded 

 into verticillate branches much longer than the leaves, each branch and each 

 pedicel subtended by 2 or 3 lanceolate papery bracts; flowers hypogynous; sepals 

 3, plane or somewhat gibbous, obtuse, green, 3-4 mm. long; petals 3, white or 

 sometimes rose to pink, 3-6 mm. long, rhombic in outline, margins entire or 

 minutely erose; stamens 6 to 9, much-surpassing the ovary; filaments glabrous; 

 anthers 0.6-1 mm. long; pistils numerous, in a single often obscurely 3-sided 

 whorl; styles 1-1.5 mm. long, as long as or longer than ovary; fruiting heads 

 more than 3.5 mm. in diameter; achenes with a solitary deep groove on back, 

 2-3 mm. long, 1.5-2 mm. wide, the beak on the inner angle, erect or suberect. 

 A. brevipes Greene, A. Plantago-aquatica subsp. brevipes (Greene) Samuelsson, 

 and var. americanum Schult. & Schult., and var. Michaletii (Asch. & Grabn.) 

 Buch. 



In shallow water or on wet mud in N.M. (Rio Arriba, Valencia and Taos cos.) 

 and Ariz. (Coconino, Navajo and Cochise cos.), May-Sept.; Que. to B.C., s. to 

 Md., W.Va., Mich., la., Neb., N.M., Ariz, and n. Mex. 



2. Echinodonis Rich. Burhead 



Annuals or short-lived perennials of wet habitats, with basal leaves and naked 

 erect or repent scapes that are sparingly branched or occasionally simple; flowers 

 pedicellate, perfect, usually in remote whorls; sepals 3, persistent; petals 3, im- 

 bricated in the bud, white, deciduous; stamens 6 to usually many more; filaments 

 elongate, usually exceeding the anthers in length; achenes forming a head, turgid, 

 ribbed or ridged, beaked or beakless. 



A dozen or more species in America, Europe and Africa. 



1. Achenes 20 or fewer in a loose head, essentially beakless; stamens 9; anthers 

 basifixed 1. E. parvulus. 



1. Achenes 30 or more in a dense tight head, prominently beaked; stamens 12 or 



more; anthers versatile (2) 



2(1). Sepals with papillose ridges; scape erect when young but soon repent; 

 achenes with summit or keel often crested and the beak ascending; 

 pellucid lines of leaves mostly 1 mm. or more apart and rarely 

 exceeding 1 mm. in length 3. E. cordifolius. 



2. Sepals with smooth veins; scape rigidly erect at maturity; achenes with keel 



entire and the beak erect or nearly so; pellucid lines of leaves 

 mostly less than 1 mm. apart and often several mm. long (3) 



3(2). Plants robust, usually much more than 2 dm. tall; leaves typically broadly 

 ovate, broadly cuneate to cordate at base; beak of achenes 1.2-2 

 mm. long 2. E. rostratus. 



137 



