530 HALORAGE^. Mtriophyllum. 



quinately verticillate, or often somewhat scattered; the lower ones pinnately 

 parted, with few and very slender capillary segments ; floral leaves linear, 

 pectinately tootlied or pinnatilid-serrate ; petals oblong ; carpels strongly 

 2-ridged on the back, the ridges tuberculate. — Michx. ! fl. 2. p. 190 ; Ell. 

 I. c. ; DC. x>rodr. 3. p. 69. Potamogeton pinnalum, Walt.! Car. p. 56. 



In shallow ponds &c. throughout the Southern and Western States ! 

 April-July. — Stems 6-12 inches" high. Bracteoles ovate, serrulate. Lobes 

 of the calyx very small, triangular-lanceolate. Petals mostly mucronate. 

 Stamens 4 (6, Elliott) : anthers oblong. Stigmas linear, heset with long 

 purple hairs. Carpels cohering at the axis; the tuberculate ridges promi- 

 nent in the mature fruit, the re-entering angles well defined ; the sides smooth 

 and even, or minutely scabrous. 



5. M. liippuroides (Nutt. ! mss.) : leaves quaternately verticillate; the 

 lower ones pinnately parted, with capillary segments ; floral leaves linear, 

 remotely denticulate or serrate ; petals obovate ; carpels nearly even, slightly 

 2-ridged on the back. — M. scabratum, Cham. 8^- Schlecht. in Linnaa, 4. 

 p. .50"6. 



Oregon, in ponds of the Wahlamet, Nuttall! California, near St. Fran- 

 cisco, Chamisso (without fruit). — Appears nearly to resemble the preceding; 

 but the fruit is very different. 



§ 3. Flowers tetrandrous : petals someiohat persistent : carpels not ridged on 

 the back: leaves alternate, or almost wanting: terrestrial or aquatic. — 

 Ptilophyllum, Nutt. (Purshia, Raf. Hylas, Bigelmo.) 



6. M. ambiguum (Nutt.) : submersed leaves pinnately parted into (about 

 10) much attenuated capillary segments ; the scarcely emersed ones pecti- 

 nate : the upper floral ones linear, tapering into a short petiole, sparingly 

 incised or toothed, sometimes entire ; flowers mostly perfect ; petals oblong ; 

 carpels smooth and even (ndnute), slightly coherent. 



a. natans : stems floating ; emersed leaves as in var. y. ; the floating ones 

 capillary.— I>C..' prodr. 3. p. 70. M. (Ptilophyllum) ambiguum, Nutt..' 

 gen. 2. p. 212. 



/?. capillaceum: leaves all immersed and capillary. — M. capillaceum, 

 Torr. ! compend. 



y. limosum (Nutt.) : small ; stems procumbent and rooting; leaves all linear 

 (rigid), sparingly toothed or lobed, often entire. — Nutt..' I. c. ; DC. I. c. 

 M. procumbens, Bigel. fl. Bost. ed. 2. j^. 346. Purshia humilis, Raf. in 

 New YorJc, med. rep. 2. p>' 361, fide icon, iiied. H^'las pinnatus, Bigel. 

 ined. fide Hook. 



In ponds and ditches (a. & /?.) and in wet miry places (y.) Massachusetts ! 

 and Long Island, New York ! to New Jersey ! and Pennsylvania ! July- 

 Aug. — Stems much branched (in y. 2-6 inches long) : the leaves scattered. 

 Flowers minute. Petals (calyx, Nutt.) persistent, purplish. Anthers 

 oblong. Stigmas penicillate. — Varies greatly in appearance, according to 

 the situation in which it grows. 



*7. M. tenellum (Bigel.) : stems (scapes) almost leafless, simple, arising 

 from a prostrate rhizoma ; floral leaves or bracts minute, entire ; flowers 

 (6-15, monoecious) alternate ; petals linear-oblong; carpels smooth and even. 

 —Bigel..' fl. Bost. ed. 2. p. 346 ; DC. ! I. c. ; Hook. .' fl. Bor.-Am. 1. p. 

 216. M. nudum, LaPylaie! ined. Hylas aphyllus, Bigel. ined. 



Borders of ponds, Newfoundland, La Pylaie ! New England States ! and 

 Northern part of New York ! July. — Scapes slender, 4-10 inches high, 

 with numerous scale-like rudiments of leaves, often 4-6 from the saiue 



