The Flora of the Cayuga Lake Basin 47 



g. Floating leaves wanting; fruit slightly 1-keeled; stems coarse. 



6. P. lucens 

 f. Submerged leaves narrowly lanceolate, evenly tapering from near the 

 base to a bluntish tip ; floating leaves spatulate, distant, all more or 

 less suffused with red ; ?>-$ carpels developing ; fruit 2.7-3 mm. long, 

 1-keeled, with a pit on the side. 7. P. alpinus 



(I. Base of submerged leaves clasping; floating leaves wanting. 

 c. Blade entire ; fruit apiculate or blunt. 



/. Leaves slightly clasping, lanceolate, rounded and cucullate at the apex, 

 (5) 10-30 cm. long; fruit sharply 3-keeled, 4-5 mm. long; ligules 

 2-8 cm. long ; stem whitish. 8. P. praclongus 



f. Leaves strongly clasping, lanceolate to ovate-orbicular, 1-8 (11) cm. 

 long, obtuse or acute ; fruit obscurely 3-keeled, 2.5-4 mm. long ; 

 ligules 1-2 cm. long; stem green. 

 g. Ligules conspicuous, at least as shreds ; peduncles spongy ; spikes 

 1.5-3.5 cm. long; fruit 3.5-4 mm. long, green, the epicarp puckered 

 in drying. 9. P. Richardsonii 



g. Ligules rarely developed; peduncles slender; spikes 0.7-2 (3) cm. 

 long; fruit 2.5-3.2 mm. long, the olive or brownish epicarp closely 

 investing the seed ; leaves usually broader, more obtuse, less nerved, 

 and darker green in drying than in the last-named species. 



10. P. bupleuroides 

 e. Blade serrulate, oblong, obtuse, crisped ; fruit with a long slender beak. 



11. P. crispus 

 c. Submerged leaves linear. 



d. Spikes all axillary ; peduncles short, 2-10 mm. long ; fruit coiled, about 1 mm. 



long ; floating leaves usually present. 12. P. dimorphus 



d. Spikes terminal or in the upper axils only, on long peduncles ; fruit not coiled. 

 e. Submerged leaves with cellular reticulation between the inner nerves, 

 2-10 mm. wide; floating leaves present; fruit 3-keeled when dry. 

 /. Submerged leaves 5-18 cm. long, rarely longer. 2-5 mm. wide, 5-7- 



nerved; floating leaves 0.7-2.4 cm. wide. 13. P. epihydrus 



f. Submerged leaves 12-22 cm. long, 5-10 mm. wide, 9-13-nerved; floating 



leaves 2.5-3 cm. wide. 13a. P. epihydrus, 



var. cayugensis 

 e. Submerged leaves without cellular reticulation, or only slightly cellular near 

 the midrib, smaller ; floating leaves absent. 

 /. Leaves many-nerved, 2-4 mm. wide ; stem wing-flattened, almost as wide 

 as the leaves ; fruit 3.5-4.5 mm. long, more or less 3-keeled. 



14. P. compressus 

 f. Leaves 3-7-nerved, 0.3-3.5 mm. wide ; stems not winged. 



g. Principal leaves 1.8-3.5 mm. wide. 



It. Nerves of the leaves 5-7; fruit 2-3 mm. long, obscurely or scarcely 

 keeled; apex of embryo not coiled; ligules 6-17 mm. long; apex 

 of leaf obtuse and mucronulate ; spikes oblong ; glands small. 



15. P. Friesii 



h. Nerves of the leaves 3 (5) ; fruit 3.5^.5 mm. long, 3-keeled; apex 

 of embryo coiled. 

 i. Ligules 0.5-1 cm. long ; leaves acute ; spikes capitate ; glands at 



base of leaves small. 16. P. Hillii 



i. Ligules 1.2-2 cm. long; leaves obtuse, mucronulate; spikes oblong; 

 glands at base of leaves large. 17. P. obtusifolius 



g. Principal leaves 0.5-1.5 mm. wide; fruit 2-3 mm. long. 



/(. (ilands at base of leaves present; peduncles much longer than the 



spikes ; fruit not keeled. 18. P. pusillus 



h. Glands at base of leaves lacking ; peduncles scarcely exceeding the 

 spikes ; fruit with a toothed keel. 19. P. foliosus 



