ONAGBACEAE. 309 



Family 6. ONAGRACEAE Dumort. 



EVENING-PRIMROSE FAMILY. 



Herbs, or rarely shrubs, with alternate or opposite leaves, no stipules 

 or mere glands in their places, and generally perfect flowers. Calyx-tube 

 adnate to the ovary, the limb 2-6-lobed (usually 4-lobed). Petals 2-9 

 (usually 4), convolute in the bud, rarely none. Stamens usually as many 

 or twice as many as the petals. Ovary 1-6-celled (usually 4-celled) ; styles 

 united; stigma capitate, discoid or 4-lobed; ovules generally anatropous. 

 Fruit a capsule or small nut. Endosperm very little or none. Forty 

 genera and about 350 species of wide geographic distribution, most abund- 

 ant in America. 



Stamens 4. 



Leaves opposite. 1. Isnardia. 



Leaves alternate. 2. Ludwigia. 



Stamens 8 T2 in 2 series. 3. Jussiaea. 



I. ISNARDIA L. Sp. PI. 120. 1753. 



Succulent herbs. Stems creeping or floating; leaves opposite, relatively 

 few, petioled. Flowers axillary, sessile, not yellow. Calyx-segments 4, shorter 

 than the tube or slightly longer. Filaments very short. Ovary very short; 

 styles often almost wanting. Capsule obovoid or turbinate, straight. [In 

 honor of Antoine Dante Isnard, a French botanist, and a member of the 

 Academy of Sciences, died 1724.] About 4 species in North America, Mexico 

 and the West Indies. Type species: Isnardia palustris L. 



1. Isnardia repens (Sw.) DC. Prodr. 3: 60. 1828. 



Ludungia repens Sw. Prodr. 33. 1788. 



Ludwigia natans Ell. Bot. S. C. & Ga. 1: 581. 1821. 



Isnardia natans Small, Fl. SE. U. S. 825. 1903. 



Stems 6 dm. long or less, branched or simple. Leaves elliptic, oval, or 

 obovate, 2-6 cm. long, acute or blunt at the apex, narrowed at the base into 

 rather slender petioles; flowers solitary, sessile or short-peduncled ; bractlets 

 linear, acute, shorter than the fruiting calyx ; calyx-lobes 4 or 5, sharply tri- 

 angular, acute, longer than the petals; capsule 6-8 mm. long, bluntly 

 tetragonal, narrowed at the base, 3 times as long as the calyx-lobes. 



Sink-holes and fresh-water swamps, Great Bahama and New Providence : 

 North Carolina to Florida, Mexico and California ; Bermuda ; Cuba ; Hispaniola ; 

 Jamaica. LARGER MARSH PURSLANE. 



2. LUDWIGIA L. Sp. PI. 118. 1753. 



Perennial or annual herbs, with alternate usually entire leaves, and axil- 

 . lary or terminal flowers. Stems erect or ascending, sometimes angled, or 

 winged. Calyx-lobes generally persistent. Petals usually 4. Stamens usually 

 4. Ovary 4 5-eelled. Capsule terete, ribbed or winged, septicidally dehiscent, 

 or opening by an apical pore. [Named in honor of C. G. Ludwig, 1709-1773, 

 Professor of Botany at Leipsic.] About 25 species, natives of warm and tem- 

 perate regions, most abundant in North America. Type species: Ludwigia 

 alternifolia L. 



