rODOSTEMACEVE. (UIVER-WEED FAMILY.) 429 



Aug. — From a few inches to a foot and more in length: upper leaves 3" -5" 

 long ; lower ones twice as long. A terrestrial form with smaller, narrower, and 

 more uniform leaves (C. brevifolia, Pursh), occurs where the waters recede in 

 summer and fall. (Eu. ) 



3. C. hetaroph^lla, Pursh. Fruit sm.allcr, as broad or broader than 

 high, deeply cmarginate, thick, almost ventricosc, sessile or nearly so, its lobes 

 obtusely angled, wiih a small groove between them ; stigmas as long as the 

 fruit, erect, persistent ; floating leaves crowded in a tuft, broadly spatulate, often 

 retuse, abruptly narrowed into a long petiole. (C. Asagrayi, Hegtimaier.) — 

 Stagnant water. New York to Illinois and southward: common. April -Aug. 

 — Similar to the last, of same size, but with smaller leaves (2" -4" long), and 

 fruit scarcely larger than in No. 1, but much thicker. A terrestrial form (which 

 comes also under C. brevifolia, Pursh) and a submerged one, with linear leaves 

 often an inch long (C. linearis, Pursh), arc not rare. 



§ 3. Submersed species. Perennials, entirely under water, with crowded and uni- 

 form linear l-nerved leaves, without scales or stomata : flowers hrarlless, fertilized 

 under tcater : filament not elowjating: carpch se/iarate nearly to the axis. 



4. C. autumn^lis, L. Fruit large, flattened, circular, deeply and nar- 

 rowly notched, sessile or nearly so, its lobes broadly winged, and with a very 

 deep and narrow groove between them ; stigmas very long, reflexed, deciduous ; 

 leaves all linear from a broader base, retuse or notched at tip. — In the St. Law- 

 rence River, near Ogdensburgh (G. W. Clinton), Lake Superior (C. G. Loring, 

 Jr.), and northwestward. Aug. -Sept. — Stems 3"- 6" high : leaves 2"- 5" 

 long : fruit variable in size, usually 1" or more in diameter. (Eu.) 



Order 96. PODOSTEIWACEiE. (River-weed Family.) 



Aquatics, growing on stones in running water, some with the aspect of 

 Sea-weeds or others of Mosses or Liverworts ; the minute naked flowers 

 bursting from a spathe-like involucre as in Liverworts, producing a 2 - 3- 

 celled many-seeded ribbed pod ; — represented in North America by 



1. PODOSTIIMON, Michx. River-weed. 



Flower solitary, pedicelled, from a tubular sac-like involucre, destitute of 

 floral envelopes. Stamens borne on one side of the stalk of the ovary, with 

 their long filaments united into one for more than half their length, and 2 short 

 sterile filaments, one on each side : anthers 2-celled. Stigmas 2, awl-shaped. 

 Pod oval, 8-ribbed, 2-celled, 2-valve(l. Seeds minute, very numerous on a thick 

 persistent central placenta, destitute of albumen. — Leaves 2-ranked. (Name 

 ivomiTovs, foot, awA (rTrnKjiv, stamen; the two stamens being apparently raised 

 on a stalk by the side of the ovary.) 



1. P. ceratoph^Uus, Michx. Leaves rigid or horny, dilated into a 

 sheathing base, above mostly forked into thread-like or linear lobes. — Not rare 

 in the bottom of shallow streams. July- Sept. — A small olive-green plant, of 

 firm texture, resembling a Sea-weed, tenaciously attached to loose stones, ia 

 the manner of a Fw.us, by fleshy disks or processes in place of roots. 



