8o 



ZANNICHELLIACEAE 



Floating leaves fewer nerved. 



Submerged leaves mostly 7-nerved, at least the 

 lowest sessile. 

 Submerged leaves serrulate at apex. 

 Submerged leaves entire. 



Plant green; submerged leaves nar- 

 rower than the floating. 

 Plant reddish, submerged leaves as 

 wide as or wider than the floating. 

 Submerged leaves more than 7-nerved; all 

 petiolate. 

 Floating leaf bases merely rounded, not 

 cordate; submerged leaves as wide as the 

 floating or nearly so. 

 Floating leaf bases cordate or sub-cordate. 

 B. With only submerged leaves. 



Leaves of a lanceolate, ovate or orbicular type, never 

 linear. 

 Leaves stalked or merely sessile, not perfoliate. 

 Without propagating buds; the elliptic-ovate 



leaves serrulate only at the apex. 

 With propagating buds; the oblong-lanceolate 

 leaves serrulate throughout. 

 Leaves perfoliate. 



Leaves cucullate; the straight apex of the 



embryo pointing towards the base. 

 Leaves not cucullate; the curved apex of the 

 embryo pointing inside the base. 

 Leaves all linear. 



Stipules adnate to the leaf bases. 



Leaves at least 1 mm. wide, serrulate. 

 Leaves capillary, less than 0.5 mm. wide, entire. 

 Stipules free from the leaf bases. 

 Leaves at least 1.6 mm. wide. 



The straight apex of the embryo pointing 



towards the base. 

 The curved apex of the embryo pointing 

 inside the base. 

 Keels of the fruit undulate or toothed. 

 Without propagating buds; leaves 



3-nerved. 

 With propagating buds; leaves 

 many-nerved. 

 Keels of the fruit smooth. 

 Leaves all capillary, less than 0.9 mm. wide. 

 Nutlets without keels or obscurely keeled. 

 Nutlets keeled, or at least with two 

 grooves culminating in three ridge 

 like keels. 

 The straight apex of the embryo 

 pointing towards the base, or out- 

 de it. 



9. P. angustifolius. 



10. P. heterophyllus. 



11. P. alpinus. 



12. P. americanus. 



13. P. pulcher. 



14. P. lucens. 



15. P. crispus. 



16. P. praelongus. 



17. P. perfoliatus. 



18. P. Robbinsii. 



19. P. pectinalus. 



20. P. foliosus. 



21. p. mm. 



22. P. compressus. 



23. P. obtusifolius. 



24. P. pusillus. 



20. P. foliosus. 



