TETRANDRIA— TETRAGYNIA. Potamogeton. 233 



thentic specimens, if they exist at Oxford^ or elsewhere, may 

 confirm or refute. 



8. P. crispum. Curled Pond-weed. Fresh-water 



Caltrops. 



Leaves lanceolate, waved, serrated, alternate; the upper 

 ones opposite. Flowers in loose spikes. 



P. crispum. Liww. % PL 182. Willd.v.\.1\^. FLBr.ldb. Engl. 

 Bot. V. 15. f. 1012. Curt. Lond.fdsc. b.t.\b. Hook. Scot. 58. 

 Fl. Dan. t.927. Br. Prodr. 343. 



P. n.848. Hall. Hist. V. 1.376. 



P. seu FontinalLs crispa. Raii Syn. 149. Bank. Hist. v. 3. 770./. 



Tribulus aquations minor, quercus floribus. Ger. Em. 824./. 



Pusillum Fonti-lapathum. Lob. Ic. v. 1 . 286./. 



/3. Potamogeton serratum. Huds. 7.5 , excl. perhaps all the syn. 



Tribulus aquaticus minor. Clus. Pann. 7lS.f. 714 ^ 715. Hist, 

 V.2. 252 f. 



T. aquat. minor, muscatellae floribus. Ger. Em. 824. f. not descrip- 

 tion. 



In ditches, ponds, and rivulets, frequent. 



Perennial. June, July. 



Whole plant under water, bright green. Leaves sessile, or nearly 

 so, 2 inches long, bluntish, elegantly crisped at the edges, and 

 more or less undulated ; furnished with slight reticulations next 

 the rib, far less remarkable than the last. The lower leaves are 

 usually alternate ; upper ones often opposite. Fl. yellowish 

 green, with elongated reddish styles, in short loose spikes. Hud- 

 son's P. serratum is acknowledged by himself to be too near 

 crispum, of which it is doubtless a variety with more of the leaves 

 opposite, and all perhaps less undulated ; as in Clusius's figure, 

 annexed by Johnson, in Gerarde, to a description belonging to 

 P. densum. 



9. P. compressum. Flat-stalked Pond-weed. 

 Leaves linear, obtuse, with a very slight point; two lateral 



ribs meeting just below the extremity. Stem compressed. 



P. compres.sum. Linn. Sp.PlAS^. IVilld. v. \.7l5. Fl.Br.\95. 

 Engl. Bot. V.6. t.4\S. Hook. Scot. 58. Fl. Dan. t. 203. 



P. caule compresso, folio graminis canini. Raii Syn. 149, Dill. 

 Giss.l\2. 



In ditches and slow stream.s. 



Perennial. June, July. 



Stem wavy, alternately branched, much compressed tliroughout its 

 whole length, though rounded at the edges. Leaves sessile, al- 

 ternate, except a })air or two of the uppermost, perfectly linear, 

 in which this species diflcrs from all the preceding ; they are 2 



