- 11 - 



drying; stipules acute; fruit 

 laterally compressed, reddish- 

 brown, not pedicelled. 



29 



29. Stem rarely or once 

 branched; submersed leaves 

 sessile (ocassional leaf 

 petiolate up to 4,0 cm 

 long), blades 5.0-20.0 cm 

 long, (7-) 9-19-veined 

 (fig. 33A) . 

 29. P^ illinoensis 



24. Submersed leaves clasping stem (figs. 33A, 34A, 

 35A) ; floating leaves absent. 



30. Rhizomes spotted with rusty red; leaves 

 ovate-oblong, (5-) 10-20 (-25) cm long 

 (fig. 34A) , apex boat-shaped (curved upward) 

 (fig. 34C) , and splitting when pressed 

 (fig. 34D) ; stipules usually persistent and 

 conspicuous. 

 30. P^ praelongus 



30. Rhizomes unspotted; leaves roundish-ovate 

 (fig. 36E) , orbicular (Fig. 36G) to 

 lanceolate (Fig. 36H) , 1-10 cm long, apex 

 flat; stipules inconspicuous (fig. 36A) or 

 disintegrating into fibers (fig. 35A) . 



31. Leaves ovate-lanceolate (fig. 35C) to 

 narrowly-lanceolate, 3-10 cm long, with 

 7-33 coarse veins; stipules coarse, 

 disintegrating to persistent white 

 fibers, even on the lower portion of the 

 stem (fig. 35A) . 

 31 . P^ r ichardsonii 



31. Leaves orbicular (fig. 36C) to ovate 

 (fig. 36G) , becoming lanceoclate in soft 

 water (fig. 36H) , 1.0-6.0 cm long, 

 0.5-2.0 cm wide, with 7-17 delicate 

 veins; stipules disintegrating and 

 absent on the lower portions of the 

 stem. 

 32. P. per foliatus 



