TETRANDRIA-TETRAGYNIA. Potamogeton. 235 

 1 1. P. graminewn. Grassy Pond-weed. 



Leaves linear, tapering downward, with solitary, very slen- 

 der, lateral ribs. Stem round, forked. Flower-stalks from 

 the forks, scarcely longer than the spikes. 



P. gramineum. Linn. Sp. PL ISA. mild. v. I. 716. Fl. Br 196 

 Engl. Bot. V. 32. t. 2253. Teesdale Tr. of Linn. Soc. v. 2 106* 

 Br.Prodr.343. 



P. gramineum latiusculum, foliis et ramificationibus densissim^ 

 stipatis. Dill, in Raii Stjn. 149. t. 4./. 3. 



In ponds and ditches. 



In ditches near Deptford. Buddie. Near Norwich. Mr. Rose. In 

 the ponds at Castle Howard, and near Beverley. Yorkshire 

 Mr. Teesdale. 



Perennial. Jalij. 



Herb submersed. Stem slender, thread-shaped, wavy, mucli branch- 

 ed, forked in the upper part. Leaves grassy, alternate, except 

 at the forks, crowded, spreading, 3 inches long, of a fine green, 

 linear, though gradually contracted toward the base, bluntish^ 

 with an occasional small short point. Their mid-rib is more or 

 less accompanied by very narrow, oblong, parallel reticulations j 

 side ribs solitary, nearer to the margin than to the mid-rib, ex- 

 tremely fine, and sometimes scarcely discernible, vanishing' at a 

 greater or less distance below the point. There are no inter- 

 mediate ribs, Stipidas pale, usually convoluted, so as to be nar- 

 rower than their leaves. Stalks from the forks of the stem, per- 

 haps without exception ■ the remark to the contrary, in some 

 instances, being founded on a specimen of P. cuspidatum, mis- 

 taken by Linnieus. Spikes ovate, dense, generally quite as long 

 as their stalks, just raised above the water. Seeds almost globu- 

 lar, with an oblique point. 



Tlie ribs of the leaves in this and the two preceding species will 

 always clearly ascertain them. They have indeed puzzled bota- 

 nists who have seen them only superficially, or not at all ; but 

 they are not the less distinct on that account. 



12. V,pusilhim. Small Pond-weed. 



Leaves linear, spreading at the base, opposite or alternate, 

 with solitary, very slender, lateral ribs. Stem round. 

 Flower-stalks axillary, mostly lateral, many times longer 

 than their spikes. 



P.pusillum. Linn.Sp. PL [84. mild. v. 1.717. I'l.Br.\07. Engl. 



Bot.v.3.t.2\D. Hook. Scot. 59. Ehrh.HerbAVl. El.Dan. t.l43[' 

 P. n, 852. Hall. Hist. v. 1. 3/7. 

 P. pusillum, gramineo folio, caule tereti. Raii Si/n. I.IO. J'aill. 



Par. 164. /.32./. 4. 



