146 COMMON CANADIAN WILD PLANTS. 



the water. Plants of no very great interest. The most obvious 

 characters of a few species are given here. 



POT AMOGE'TOtf , Touru. PONDWK i . i .. 



1. P. natans, L. Submersed leave* (jraxx-like. or cnjiif/ar// : 

 upper stipules very long, acute. Spikes cylindrical, all out of the 

 water. Stem hardly branched. Floating leaves long-}><'(io/<;/, 

 elliptical, with a somewhat heart-shaped base, with a blunt apex, 

 21-29-nerved. 



2. P. Claytonii, Tuckerman. Stem compressed. Submersed 

 leaves linear, 2-5 inches long, 2-ranked, 5-nerved ; stipules 

 obtuse. Floating leaves short- petioled, chiefly opposite, oblong, 

 11- 17 -nerved. Spikes all above water. 



3. P. amplifo'lillS, Tuckerman. Submersed leaves large, 

 lanceolate or oval, acute at each end, recurved, wavy ; sfi/mfr* 

 long and tapering. Floating leaves large, oblong or lance-ovate, 

 or slightly cordate, long-petioled, 30-50-nerved. 



4. P. gramin'eilS, L. Submersed leaves lanceolate or linear- 

 lanceolate, upper ones petioled, lower ones sessile. ///>/<* 

 obtuse. Floating leaves with a short blunt point, 9-15-nerved. 

 Var. heterophyTlllS, Fries., (the common form) has the lower 

 leaves shorter, lanceolate, and more rigid. 



5. P. lucens, L. , var. minor, Xolte. Leave* all submersed, 

 more or less petioled, oval or lanceolate, mucronatt, ^/lining. 

 Stem branching. 



6. P. perfolia'tUS, L. Leaves all submersed, varying in width 

 from orbicular to lanceolate, clasping by a hea/i-*/i<tj>(<l l<i*f. 

 Stem branching. 



7. P. COmpreSSUS, Fries. (P. tOSterCRfoUm, Schum., in Ma- 

 coun's Catalogue.) Leaves all submersed, linear, grass-like, 

 sessile, with three large nerves and many fine ones, 

 branching, iving -flattened. Stipules free from the sheathing base 

 of the leaf. 



8. P. pectina'tus, L. Leaves all submersed, bristle-shaped. 

 Stem repeatedly forking, filiform. .S/>/7iVx int< ///!/>//, on l<><j 

 slender peduncles. Stipules united with the sheathing base of the 

 leaf. 



