6 NORTH AMERICAN FLORA [V01.UME 22 



2-valved, the valves unequal and 5-nerved, the one deciduous with the placenta and seeds, 

 the other persistent. 



Flowers single or scattered : stems usually less than 1 dm. long : leaves short 



and narrow. 1. P. Cera top hy Hum. 



Flowers clustered at the end of the stem : stems usually more than 2 dm. 



long, sometimes reaching 8 dm.: leaves long and filiform. 2. P. abrotanoides. 



Type species, Podostemon Ceratophyllum Michx. 



1. Podostemon Ceratophyllum Michx. Fl. Bor. Am. 2: 165. 1803. 



Lads ceratophylla Bong. Mem. Acad. Petersb. VI. 3^ : 78. 1835. 



Stems less than 2 dm. long, usually but a few centimeters, simple or somewhat 

 branched. Leaves very narrow, entire or dichotomously dissected ; pedicel less than 1 cm. 

 long; flowers single or scattered; capsule 2.5-3 mm. long, ellipsoid, obtuse. 



Type locality : Ohio River, near I^uisville. 



Distribution : Maine to Ontario, Kentucky, Georgia and Alabama. 



Illustrations: Michx. Fl. Bor. Am. 2: pi. 44 ; Britt. & Brown, 111. Fl. /. 1808 ; Torr. Fl. 

 N. Y. pi. 98; Schnitzl. Icon. pi. 85, f. 8-22; Vidensk. Selsk. Skr. VI. Nat. og Mat. 2 : pi. 1-3, pi. 

 4,f, 1-13, pi. 7 ; Hook. Comp. Bot. Mag. 2 : pi. 20. 



2. Podostemon abrotaaoides Nutt. Jour. Acad. Phila. 7: 105. 1834. 



Stems commonly 2-S dm. long, more branched than in the preceding. Leaves finely 

 dissected, the ultimate divisions long and filiform ; flowers clustered at the end of the 

 stem or branches; capsule 2.5-3 mm. long, ellipsoid. 



Type locality : Chattahoochee River, Georgia. 

 Distribution : Georgia and Florida to Mississippi. 



5. OSERYA Tul. & Wedd. Ann. Sci. Nat. III. 11 : 105. 1849. 



I 



Small aquatic plants creeping on inundated rocks, with a simple or branched rhizome, 

 distichous simple or dissected leaves, and usually terminal solitary flowers. Flowers with 

 a rudimentary perianth, at first enclosed in a spathe which is finally disrupted by the pedicel. 

 Stamen 1 ; filament flattened. Ovary obliquely sessile, 2-celled. Stigmas 2, erect, free, 

 very short. Capsule of 2 unequal nerved valves, the larger persistent, the smaller deciduous. 



Type species, Oserya flabellifera Tul. & Wedd. 



1. Oserya Coulteriana Tul. Ann. Sci. Nat. III. 11 : 106. 1849. 



Rhizome flabelliform, the stems 2-3 cm. long, simple or dichotomously branched. 

 Leaves 3-6 cm. long, the blade dichotomously dissected, the divisions very narrow ; flowers 

 solitary, usually at the summit of the stem, rarely from the axils or from the rhizome 

 itself ; stamen 1 ; ovary smooth or sometimes inconspicuously striate ; mature capsule 

 unknown. 



Type locality : San Bias to Guadalajara, Mexico. 

 Distribution : Mexico. 



