Fig. 58: Echinodorus rostratus: a, head, X 5; b, achene, X 25; c, seed, X 60. 

 (Courtesy of R. K. Godfrey). 



3. Plants delicate, rarely more than 2 dm. tall; leaves typically lanceolate, nar- 

 rowly cuneate to somewhat rounded at base; beak of achenes 0.5-1 

 mm. long 2. E. rostratus var. lanceolatus. 



1. Echinodorus parvulus Engelm. Fig. 56. 



Plants small and delicate, with the shoots often creeping and proliferous; scapes 

 to 1 dm. tall, supporting a single umbellate inflorescence of 2 or more flowers; 

 leaves with a petiole to 5 cm. long, the blade (to 3 cm. long and 8 mm. wide) 

 narrowly elliptic and acutely tapered at both ends; pedicels slender, to 3 cm. long, 

 reflexed in fruit; flowers white, about 6 mm. across; achenes 8-ribbed, reddish- 

 brown, glandless. E. tenellus var. parvulus (Engelm.) Fassett, Helianthium par- 

 vulum (Engelm.) Small. 



Among grasses in wet sandy soils about ponds in s. Tex., Mar.-Sept.; from Fla. 

 and Tex., locally n. to Mass., 111. and Mo. 



2. Echinodorus rostratus (Nutt.) Engelm. Figs. 57 and 58. 



Plants usually coarse; scapes rigidly erect, to 6 dm. tall, exceeding the leaves; 

 leaves broadly ovate, cordate to broadly rounded-cuneate at base, obtuse at apex, 

 to 15 cm. long and often as broad; umbels proliferous, in a branched panicle; 

 flowers white, about 1 cm. across; achenes with 2 glands at base of the conspicu- 

 ous erect beak; seeds brown, obliquely oval, with rows of murications. E. cordi- 

 folius, misapplied; E. Berteroi (Spreng.) Fassett, as to descr. 



In mud and shallow water about lakes, ponds and along streams mostly in s. 

 Tex. but sparingly throughout most of the state, in Okla. (Alfalfa and Kay cos.) 

 and apparently isolated in Yuma Co., Ariz., May-Oct.; from Ont., w. to Calif, 

 and s. to Fla., Tex. and Mex. 



139 



