33 
Pl. end.ph. 6. FLU VI AT. 25. Ruppia. 
Potamogiton maritimum gramineis longioribus foliis, fructu fere umbel- 
lato, Raii Syn . 134. 
Bucca ferrea maritima, foliis acutissimis, Mich.N.P. G. 72. 
Ruppia maritima, Lin. 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 ; perigonium 4 -parted ; stamens 4 : fila- 
ments flat, short; anthers 2-celled; ovaries 4, oval, pointed; 
nut 1-seeded, sessile. — Leaves mostly alternate ; floral leaves 
sometimes opposite ; spike terminal or axillary. 
a. Leaves of 2 sorts, l. floating, opake , convex ; 2. under 
water. 
1 . Potamogiton natans. Floating riverweed. 
Upper leaves elliptical, petiolate, acute; base roundish 
cordate, floating ; lower leaves linear, submersed. 
Pot. rotundifolium, Raii Syn. 148, 1. 
Pot. latifolium, Ger. 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 brae- 
tese at the base ; spike simple, above water ; flowers dirty- 
green. 
0. terrestris. Sheath of the peduncle less than half its 
length. 
2. P. heterophyllum. Various-leaved riverweed. 
Upper leaves floating, petiolate, elliptical, oblong, acute, 
membranaceous, narrowed at both ends ; lower leaves under 
water, crowded, sessile, linear lanceolate.- 
Pot. gramineum, FI. Danica , 222. 
Pot. palustre, Teesdale , Tr. L. S. 5, 43. 
Pot. crassipes, Kartach. 
Pot. distachyos, Bellard. 
Pot. hybrid um, Thuill. FI. Par . 
Pot. natans y, Lam. Illustr. 
Pot. heterophyllum, Schreb. 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 
