Var. lanceolatus Engelm. Plants small and delicate, with typically lanceolate 

 leaves. Echinodorous Berteroi var. lanceolatus (Engelm.) Fassett, as to descr. 

 Habitat and distribution similar to that of var. rostratus. 



In deeper water the plants rarely produce normal adult foliage leaves and never 

 flower, but develop large, ribbonlike submersed leaves. 



3. Echinodorus cordifolius (L.) Griseb. Figs. 59 and 60. 



Plants coarse and usually stout; scapes prostrate, arching and creeping, to 12 

 dm. long, proliferous and bearing numerous whorls of flowers, also sometimes pro- 

 ducing leaves with the flowers; leaves with a petiole to 2 dm. or more long, the 

 blade (to 2 dm. long and nearly as broad) broadly ovate and truncately cordate at 

 base and obtuse at apex; flowers white, 12 mm. or more across; achenes with the 

 keeled back denticulate. E. radicans (Nutt.) Engelm. 



In mud and shallow water of ponds and quiet streams of e. Tex. and e. Okla. 

 (LeFlore and Muskogee cos.), Apr.-June; from s.e. Va., 111., Mo. and Kan., s. 

 to Fla., Tex. and Mex. 



3. Sagittaria L. Arrowhead 



Paludal or aquatic mostly perennial erect or lax stoloniferous herbs, with milky 

 juice, monoecious or rarely dioecious, sometimes tuber-bearing; leaves submersed 

 or emersed, with long cellular petioles, bladeless (i.e., phyllodia) or with unlobed 

 or sagittate blades; scapes erect or laxly ascending, sheathed at base by the bases 

 of the leaf petioles, supporting a narrow verticillate inflorescence that is simple or 

 sparingly branched; flowers produced all summer, pedicellate, in whorls of three, 

 mostly unisexual, subtended by membranous bracts, the staminate flowers typically 

 uppermost in the inflorescence; sepals 3, persistent, in fruit appressed, loosely 

 spreading or reflexed; petals 3, white or rarely pink, imbricated in the bud, usually 

 exceeding the sepals, deciduous; stamens whorled, mostly numerous; carpels 

 numerous, spirally arranged in a crowded spherical head on a dome-shaped re- 

 ceptacle, 1-ceUed and 1-ovuled; achenes flattened, membranous-winged, more or 

 less beaked. 



About 20 species, mostly in America. 



1. PistiHate flowers (in fruit) with sepals appressed or spreading and pedicels 

 recurved and noticeably thickened 1. S. montevidensis. 



1. Pistillate flowers (in fruit) with reflexed sepals and pedicels ascending or (if 



recurved) not noticeably thickened (2) 



2(1). Filaments pubescent or minutely scaly (3) 



2. Filaments smooth (5) 



3(2). Bracts of inflorescence thinly membranous, smooth, more or less connate; 

 filaments dilated (4) 



3. Bracts of inflorescence somewhat thickened, papillose or coarsely ridged, 



nearly free; filaments linear 4. S. lancifolia. 



4(3). Pistillate pedicels ascending, if recurved the achene beak less than 0.3 mm. 

 long; leaves typically narrow 2. S. graminea. 



4. Pistillate pedicels recurved; subulate beak of mature achenes 0.3 mm. or more 



long; leaves typically broad 3. S. platyphylla. 



5(2). Bracts of inflorescence papillose; leaves never sagittate (6) 



5. Bracts of inflorescence smooth or at most pubescent; leaves sagittate (7) 



6(5). Bracts densely papillose, 7 mm. long or less, obtuse; achenes 1.5 mm. long 

 or less; Texas in our area 5. S papillosa. 



6. Bracts sparsely papillose, longer, attenuate; achenes larger; Oklahoma in our 



area 6. S. ambigua. 



142 



A 



