PL end.pL 6. FLUVIAT. 25. Ruppia. S3 



Potainogiton maritimum gratnineis longioribusfoliis, fructu fere umbel- 

 lato. Rail Syn. 134. 



Bucca ferrea maritima, foliis acutissimis, Mich. N. P, G. 72. 

 Ruppia maritima, JLiH. S. P. 184, 



Salt water ditches ; perennial? July. 

 Flowering spike above the water, the peduncles lengthen- 

 ing as the depth of water requires. 



III. 26. POTAMOGITON. Dioscorides. Riverweed. 



Flowers hermaphrodite, spiked ; spikes furnished at the 

 base with 2 spathes ; pejigonium 4 -parted; stamens 4 : Jila- 

 menis flat, short ; anthers 2-cened ; ovaj'ies 4, oval, pointed ; 

 nut 1 -seeded, sessile. — Lea?;^.? mostly alternate ; floral leaves 

 sometimes opposite ; spike terminal or axillary. 



a. Leaves of 2 sorts^ l.floatifig, opake^ convex; 2. under 

 water. 



1. Potamogiton nafans. Floating riverweed. 

 Upper leaves elliptical, petiolate, acute; base roundish 



cordate, floating ; lower leaves Ihiear, submersed. 



Pot. rotundifolium, Raii Stjn. 148, 1. 



Pot. latifolium, Ge?". em. 821. 



Fontinalis major latifolia vulgaris, Park. 1254. 



Potamogiton natans, Lin, S. P. 182. 



Rivers and ponds ; perennial ; June. 



Stem very long, leafy ; peduncle single, with linear brac- 

 teaa at the base ; spike simple, above water ; flowers dirty- 

 green. 



(S. terrestris. Sheath of the peduncle less than half its 

 length. 



2. P. heterophyllum. Varions-leaved riverweed. 

 Upper leaves floating, petiolate, elliptical, oblong, acute, 



membranaceous, narrowed at both ends; lower leaves under 

 water, crowded, sessile, linear lanceolate. 



Pot. sraraineum, Fl. Datiica, 222. 



Pot. ipalustre, Teesdah, Tr. L. S. 5, 43. 



Pot. crassipes, Kartach. 



Pot. distachyos, Bellard. 



Pot. hybridum, IViuill. Fl. Par. 



Pot. na.tans ■ , Lam. Illustr. 



Pot. heterophyllum, Sckreb. Spic. 21, 



Ponds and ditches ; perennial ; July to September. 

 Stem much branched, leafy ; leaves pale green, scored ; 

 Sheaths oblong, bluish ; spike greenish. 



VOL, II. D 



