TETRANDRIA— TETRAGYNIA. Ruppia. 257 



the stipula, whose cloven summit vises 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 jnst above the surface, seldom 

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

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

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

 considerable in rapid streams, where the flowers seldom appear. 

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

 jiowers largest, in salt-water ditches j but this is disproved by 

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

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

 even as a variety. 



82. IIUPPIA. Ruppia. 



Linn. Gen. 68. Jiiss. 19. Fl. Br. 198. Lam. t. 90. Gartn. i. 81. 

 Buccaferrea. Mich. Gen. t. 35. 



Nat. Ord. see n. 81. 



Cal. and Cor. none. A^ith. 4, sessile, irregularly quadran- 

 gular, depressed, bursting by a horizontal transverse fis- 

 sure. Germens 4, occasionally 5, turbinate, at length 

 stalked. Styles none. Stigmas obtuse, depressed in the 

 centre. Seeds 4, naked, ovate, obliquely pointed, convex 

 at one side, bluntly keeled at the other, each elevated on 

 a stalk, 4 or 5 times its own length. 



Habit of Potamogeton, from which it differs in the want of 

 a corolla, in the posture as well as shape of the anthers., 

 and in the stalked seeds. But Linnaeus surely errs in using 

 the term spadix here, for what the former genus shows 

 to be ajlower-stalk. Impregnation in Ruppia takes place 

 within the sheath of the leaf, and the seeds are subse- 

 quently raised above the water to ripen ; just the reverse 

 of Potamo"eton. 



"t,"- 



1. R. maritima. Sea Ruppia. Tassel Pond-weed. 



R. maritima. Linn. Sp. PL 184. Willd. v. 1. 717. Fl. Br. 198. 



Engl. Bot. V. 2. t. 136. Hook. Land. t. 50. Scot. 59. Light/. 124. 

 ^ 8./. ] . Dicks. H. Sicc.fasc. 17.9. 

 Potamogiton maritimum, gramineis longioribus foliis, fructu ferfe 



umbellato. Raii Syn. 134. t. 6.f. 1. 

 P. maritimum pusillum alteram. Pluk. Phijt. t. 248./. 4. 

 Fucus ferulaceus. Ger. Em. \573.f. 

 Tassel Pond-weed. Petiv. H. Brit. t. G.f. 1. 

 Buccaferrea maritima, foliis acutissimis j etiam foliis miniis acutis. 



Mich. Gen. 72. t. 35. 



