TETRANDRIA— TETRAGYNIA. Potamoffeton. 237 



»• 



stance below the point, and not quite both together. Stipulas 

 sheathing, broader than the leaves. Flower-stalks lateral, axil- 

 lary j the uppermost sometimes surmounted by a pair of branches j 

 all much longer than the small, ovate spike, which consists of 

 but few Jlowers, becoming a little distant as the fruit advances. 

 Seeds ovate, obliquely beaked. 

 A perfectly clear and well-known species, though Willdenow has 

 misquoted Haller, and Haller the Fl. Dan. A variety somewhat 

 larger than common, but not otherwise different, was found by 

 Mr. Teesdale, near Beverley, which I have from Switzerland for 

 compression, and it is also marked Haller's n. 85 1 ; a combina- 

 tion of errors, for which the accurate Mr. Davall is not respon- 

 sible, for he had studied this genus correctly. 



13. P. pectinatum. Fennel-leaved Pond-weed. 



Leaves bristle-shaped, single-ribbed, parallel, thickly set in 

 two ranks; sheathing at the base. Spikes interrupted. 



P. pectinatum. Linn. Sp. PL 183. Willd. v. 1. 715. Fl. Br. 197. 

 Engl. Bot. v. 5. t. 323. Hook. Scot. 59. Ehrh. Herb. 1 23. 



P. marinum. Linn. Sp. PI. 1S4. mild. v. 1.716. Huds. 76. Fl. 

 Dan. t. 186. 



P. n. 853. Hall. Hist. v. 1. 377. 



P. millefolium, seu foliis gramineis, ramosum. Raii Syn. 150. 



P. maritimum, grandiusculis capitulis, capillaceo folio, nostras, 

 Pluk. Almag. 305. t. 216./. 5. Dill, in Raii Syn. 150. 



P. pusillum fluitans. Bocc. Sic. 42. t. 20./. 5. 



P. ramosum foliis gramineis. Vaill. Par. 164. t. 32./. 5. 



Millefolium tenuifolium. Ger. Em. 828./. 



In rivers, ditches and ponds, whether of fresh or salt water. 



Perennial. July. 



Root tuberous, with creeping scyons. Stems very much branched, 

 various in length, leafy, zigzag. Leaves alternate, two-ranked, 

 slender, tapering, acute, their solitary rib connected by trans- 

 verse alternate veins with the margins ; clasping the stem with 

 their elongated sheathing base, which appears to be lined with 

 the stipula 3 whose cloven summit rises a little above the sheath, 

 as in grasses. Spikes few, solitary, each from one of the upper- 

 most forks of the branches, on a longish stalk, cylindrical, with 

 considerable interruptions, rising just above the surface, seldom 

 produced but in still waters. Fl. 2 or 3 together, dull green. 

 Seed scarcely more than 1 or 2 from each flower, gibbous. 



Few plants vary more in the size of its herbage, which is most 

 considerable in rapid streams, where the flowers seldom appear. 

 Dillenius says the leaves are most slender, and the heads of 

 Jlowers largest, in salt-water ditches ; but this is disproved by 

 observation in England, and by Swiss specimens, all from fresh 

 water, as various as any ; so that P. marinum cannot be marked 

 even as a variety. 



