246 PONTEDERIACEAE 



frond usually unsymmetrieal, tapering into a short stipe or frequently sessile ; 

 fruit long-ovate, jiointed hy the long, straight or rarely curved style ; seed 12 to 

 29-ribbed. 



Springs and pools. North and South America. 



Loes. — Springs at foot of Uncle Sam Mt. (Mt. Konokti), Lake Co., Butaiidcr 2662; Santa 

 Cruz (Engler, Jahrb. 21:298). 



Refs. — Lemna cyclostasa Chev. Fl. Par. 2:256 (1827). L. minor var. cycloslasa Ell. Bot. 

 S. Car. and Ga. 2:518 (1824). L. valdiviana Phil. Linnaea 33:239 (1864). 



5. L. minima Phil. Fronds cohering in 2s, sometimes in 4s, or solitary, 

 oblong to elliptical, symmetrical, i L' to VA lines wide, % to 2 lines long, rather 

 thick, with a row of papillae along the mid-nerve ; lower surface flat or slightly 

 convex, upper surface slightly to prominently convex with thin margin entirely 

 around the frond ; frond cavernous in the middle portion only, commonly nerve- 

 less; seed oblong, pointed, about 16-ribbed. — Two growth stages: smaller fronds 

 straw-yellow or pale green and strikingly convex on the upper surface ; larger 

 fronds thinner and green-colored. 



Pools, California, ea.st to Wyoming and Florida. 



Loes. — San Bernardino (Erytliea, 7:90); San Francisco (Engl., Jahrb. 21:299). 



Ref.— Lemna minima Phil. Linnaea, 33:239 (1864), type from Chile. 



3. WOLFFIELLA Hglm. 

 Fronds minute, thin, band-like or ligulate, somewhat curved, rootless. Re- 

 productive pouch one, triangular, opening as a cleft in the basal margin of the 

 frond. Flowers and fruit unknown. Stipe of the daughter frond attached on 

 the margin of the reproductive pouch. — Species about 7, mostly in the tropics. 

 (Diminutive of Wolffia.) 



Fronds saber-shaped 1. W. oblonga. 



Fronds ligulate 2. W. lingulata. 



1. W. oblonga Hglm. Fronds solitary or in pairs, rarely 3s, slightly fal- 

 cate, tapering from the rounded base to the somewhat narrower rounded apex, 

 sometimes oblong, rarely straight, li/o to 21,4 Hues long. 



Southern California. Mexico, South America. 



Loc. — San Bernardino Valley (ace. Thompson, Rep. Mo. Bot. Gard. 9:39). 

 Refs. — WOLFFIELLA OBLONGA Hglm. Engler, Bot. Jahrb. 21:303 (1895). Lemna oblonga 

 Phillipi, Linnaea, 29:45 (1857), type loc. Santiago, Chile, PJiilippi. 



2. W. lingulata Hglm. Fronds solitary or in pairs, ovate to oblong-ligulate, 

 11/4 to 3t4 lines long. 



Kern Co. ; San Bernardino Vallej'. Mexico. 



Loes. — Kern Co. (ace. Thompson, Rep. Mo. Bot. Card. — 1897) ; San Bernardino Valley 

 (Erythea 7:90). 



Refs. — WOLFFIELLA LINGULATA Hglm. Engler, Bot, Jahrb. 21:303 (1895). Wolffla lingulata 

 Hglm. Monog. Lemnae, 132 ,(1868). 



PONTEDERIACEAE. Pickerel Weed Family 

 Aquatic herbs. Perianth with a tube, 6-lobed or 6-parted. Stamens 3 or 6, 

 inserted on the throat of the perianth. Ovary superior, 1 or 3-celled. — Genera 

 5 and species about 24, all continents except Europe, mostly in the tropics and 

 warm temperate regions. 



Bibliog.— Solms-Laubaeh, Poutederiaceae (DC. Monog. Phan. 4:501-535,-1883). 



1. HETERANTHERA R. & P. 



Ours submerged grass-like lierbs, only tlie flowers reaching the surface. 

 Spathe 1-flowered. Periantli with elongated filiform tube and rotate 6-parted 

 limb; segments linear-lanc(>olate. Stamens 3. Ovary 1 -celled with 3 parietal 

 placentae. — Species 9, North and South America, Africa. (Greek heteros, dif- 

 ferent, and anthera, anther, the stamens unequal in some species.) 



1. H. dubia MacM. Leaves linear or ribbon-like, translucent; perianth small, 

 pale yellow, its tube al)out 4 inches long. 



