VOL. II.] 



RIVER-WEED FAMILY. 



.163 

 I8 3 6. 



Family 37. PODOSTEMACEAE Lindl. Nat. Syst. Ed. 2, 190. 



RIVER-WEED FAMILY. 



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

 poorly differentiated 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 membranous calyx. Stamens hypogynous, 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 numerous, minute, without endosperm; embryo straight. 



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



i. PODOSTEMON Michx. Fl. Bor. Am. 2: 164. pi. //. 1803. 



Habit of the several species 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-celled; stigmas 2, nearly erect, short, 

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



About 12 species of rather wide geographic distribution. 



i. Podostemon Ceratophyllum Michx. 



River- weed. Thread-foot. 



(Fig. 1808.) 



Podostemon Ceratvphyl/ntn'M.ichx. 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 \" 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. 



In shallow streams, Massachusetts to northern New 

 York, Ontario and Minnesota, south to Georgia, Ala- 

 bama and Kentucky. July-Sept. 



Family 38. CRASSULACEAE DC. Fl. Franc. 4: 382. 1805. 



ORPINE FAMILY. 



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

 or rarely solitary regular or symmetrical flowers. Stipules none. Calyx per- 

 sistent, free from the ovary or ovaries, 4~5-cleft or 4~5-parted in our species. 

 Petals equal in number to the calyx-lobes, distinct, or slightly united at the 

 base, usually persistent, 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 mem- 

 branous or coriaceous, i -celled, dehiscent along the ventral suture. Seeds 

 minute; endosperm fleshy; embryo terete; cotyledons short, obtuse. 



About 15 genera and 500 species, of wide geographic distribution. 



