246 



PONTEDERIACEAB 



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

 fruit long-ovate, pointed by the long, straight or rarely curved style ; seed 12 to 

 29-ribbed. 



Springs and pools. North and South America. 



Locs. Springs at foot of Uncle Sam Mt. (Mt. Konokti), Lake Co., Bolandcr 2662; Santa 

 Cruz (Engler, Jahrb. 21:298). 



Eefs. LEMNA CYCLOSTASA Chev. Fl. Par. 2:256 (1827). L. minor var. cyclostasa 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, 1/2 to 1*4 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, east to Wyoming and Florida. 



Locs. San Bernardino (Erythea, 7:90); San Francisco (Engl., Jahrb. 21:299). 



Eef. 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, 1% to 2 1 / 4 lines long. 



Southern California. Mexico, South America. 



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

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

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



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

 114 to 314 lines long. 



Kern Co. ; San Bernardino Valley. Mexico. 



Locs. Kern Co. (ace. Thompson, Rep. Mo. Bot. Gard. 1897) ; San Bernardino Valley 

 (Erythea 7:90). 



Refs. WOLFFIELLA LINGULATA Hglm. Engler, Bot. Jahrb. 21:303 (1895). Wolffia 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, Pontederiaceae (DC. Monog. Phan. 4:501-535, 1883). 



1. HETERANTHERA R. & P. 



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

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

 limb; segments linear-lanceolate. 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 smal 

 pale yellow, its tube about 4 inches long. 



