204 ORDER I. RANTJNCTJLACE^E. 



nia numerous, ovate, pointed, compressed, smooth, striated, or 

 tuberculated, arranged in a cylindric or globose head. 



1. R. aquat'ilis, (L.) Stem floating, long, slender, jointed. Leaves 

 submersed, capillary, alternate, petioled. Calyx glabrous. Petals 

 white ; claw yellow, with a conspicuous pore. Achenia transversely 

 wrinkled. — ^ . June to Aug. Ponds and streams. Car. and Geo. 



a. Leaves undivided, flowers yellow, carpels smooth. 



2. R. laxicau'lis, (T. & G.) Stem weak, much branched, declined, 

 rooting at the lower joints, glabrous. Leaves smooth, linear-lanceolate, 

 or elliptical, oblong ; upper ones linear. Peduncles opposite the leaves, 

 1 — 2 inches long. Carpels with a subulate beak in a globular head. 

 Petals much longer than the calyx, slender at the base. — ^ . Ditches 

 Car. and Geo. July. 



3. R. fusil'lus, (Poir.) Stein decumbent, little branched, glabrous. 

 Leaves on long petioles, entire or denticulate, obtuse ; lower ones 

 ovate or subcordate ; upper ones linear-lanceolate. Peduncles opposite 

 the leaves, 1-flowered. Sepals ovate, obtuse. Flowers small. Petals 

 small, nearly round. Pore at the base of the limb of the petal. Sta- 

 mens few. Styles none. Achenia ovate. — Yellow. *> . Very common 

 in wet soils. March. 



b. Leaves divided. 



4. R. aborti'vus, (L.) Stem glabrous, simple, or branching. Radi- 

 cal leaves on petioles, cordate, reniform, or broadly ovate ; sometimes 

 3-parted, crenate ; cauline ones 3 — 5-parted, with long, entire, linear 

 lobes. Sepals glabrous, reflexed, longer than the petals. Flowers small, 

 scale large. Carpels in a globose head. — ^ . Common in the middle 

 regions of Geo. and Car. May. 



5. R. scelera'tus, (L.) Root fibrous. Stem 1 — 2 feet high, fistulous, 

 thick, leafy. Leaves on petioles, lower ones with petioles 4 or 5 inches 

 long, sheathing, 3-parted, radical ones with the divisions 3-lobed and 

 obtusely incised, upper ones with oblong linear entire lobes. Sepals 

 reflexed, colored. Flowers small, solitary, generally opposite the leaves; 

 petals longer than the sepals, shining. Stamens 12 — 15, shorter than 

 the petals. Carpels small, numerous, in a cylindrical head. — ^ . Com- 

 mon in the low country. May. 



6. R. Pur'shii, (Richards.) Submerged leaves filiformly, 2 or 3- 

 chotimously dissected, with segments flat ; emersed ones reniform, 3 — 

 6-parted, the lobes variously divided. Petals twice as large as the re- 

 flexed sepals. Carpels in globose heads, smooth, with a short and 

 straight ensiform style. — In ponds and muddy places. N. Car. and 

 Lou. Torrey <fe Gray. 



7. R. re'pens, (L.) Stems prostrate and creeping, sometimes erect. 

 Leaves trifoliate, segments cuneate, 3-lobed, incisely toothed, middle 

 one petioled. Calyx spreading. Carpels with a straight point. This 

 plant is very variable : sometimes villous, at others glabrous. Flowers 

 vary in size, and number of petals from 6 — 8. The R. Nitidus of 

 Elliott, we believe, is only a variety of this, as we have seen it assuming 

 all the peculiarities of that plant, with good reason to believe it was 

 the one described. — In wet grounds, very common in Middle Geo. 



8. R. palma'tus. Carolinia'nus. Stem erect, 12 — 18 inches high, 

 hairy, hair above appressed, below spreading ; branches long, 1 -flowered, 



