Genus i. 



RIVER-WEED EAMILY. 



205 



Family 43. PODOSTEMACEAE Lindl. Nat. Syst; Ed. 2, 190. 1836. 



RivER-vvEED Family. 



Small aquatic fresh-water mostly annual fleshy herbs, the leaves usually poorly 

 diflferentiated from the stem, the whole structure commonly resembling the thallus 

 of an alga or hepatic, the small usually perfect flowers devoid of any perianth and 

 subtended by a spathe-like involucre, or in some genera with a 3-5-cleft mem- 

 branous calyx. Stamens liypog}nous, only 2 in the following genus, numerous in 

 some others ; filaments united or distinct ; anthers 2-celled, the sacs longitudinally 

 dehiscent. Ovary stalked or sessile, 2-3-celled ; ovules usually numerous in each 

 cell, anatropous ; styles 2 or 3, short. Capsules 2-3-celled, ribbed. Seeds numer- 

 ous, minute, without endosperm ; embryo straight. 



About 21 genera and 175 species, mostly in the tropics, only the following North American. 



I. PODOSTEMUM Michx. FI Bor. Am. 2: 164. pi. 44. 1803. 



Habit of the several speeies various. Flowers sessile or very nearly so in the spathe-like 

 involucre. Perianth none. Stamens 2, their filaments united to near the summit ; anthers 2, 

 oblong or oval. Staminodia 2, filiform. Ovary ovoid, 2-cened ; stigmas 2, nearly erect, short, 

 subulate. Capsule ovoid, 6-io-ribbed, 2-valved. [Greek, stalked-stamens.] 



About 12 species of rather wide geographic distribution, the following typical. Besides the 

 following, another occurs in the southern United States. 



I. Podostemumceratophy Hum Michx. River- 

 weed. Thread-foot. Fig. 2130. 



Podosiemitm ceratophylhtni Mich.x. Fl. Bor. Am. 2 : 165. 

 1803. 



Plant dark green, rather stiff, firmly attached to 

 stones in running water, densely tufted, I'-io' long, 

 the leaves narrowly linear, sheathing at the base, 

 commonly split above into almost filiform segments 

 or lobes. Flowers less than i" broad, at length 

 bursting from the spathes; capsule oblong-oval, 

 rather more than i" long, obtuse, borne on a stipe 

 of about its own length, 8-ribbed ; stigmas at length 

 recurved. 



Firmly attached to stones in shallow streams, New 

 Brunswick to Ontario and Minnesota, south to Georgia. 

 .Mabama and Kentucky. July-Sept. 



Fatnily 44. CRASSULACEAE DC. Fl. Franc. 4: 382. 1805. 



Orpine Family. 



Herbs, or somewhat shrubby plants, mostly fleshy or succulent, with cymose 

 or rarely solitar\- regular or s}'mmetrical flowers. Stipules none. Calyx per- 

 sistent, free from the ovary or ovaries, mostly 4-5-cleft or 4-5 -parted. Petals 

 equal in number to the calyx-lobes, distinct, or more or less united, usually per- 

 sistent, rarely wanting. Stamens of the same number or twice as many as the 

 petals; filaments filiform or subulate; anthers longitudinally dehiscent. Receptacle 

 with a scale at the base of each carpel. Carpels equal in number to the sepals, 

 distinct, or united below; styles subulate or filiform; ovules numerous, arranged 

 in 2 rows along the ventral suture. Follicles membranous or coriaceous, i-cclled, 

 dehiscent along the ventral suture. Seeds minute; endosperm fleshy; embryo 

 terete ; cotyledons short, obtuse. 



.^bout ,30 genera and 600 species, of wide geographic distribution. 



