594 ONAGRACEAE (EVENING PRIMROSE FAMILY) 



ONAGRACEAE (EVENING PRIMROSE FAMILY) 



Herbs, with ^-merous (sometimes 2-3- or 5-6-merows) perfect and symmetrical 

 flowers the tube of the calyx adhering to the 2^-celled ovary, its lobes valvate 

 in the bud or obsolete; the petals convolute in the bud, sometimes wanting ; and 

 the stamens as many or twice as many as the petals or calyx-lobes, inserted on 

 the summit of the calyx-tube. Style single, slender ; stigma 2-4-lobed or capi- 

 tate. Pollen-grains often connected by cobwebby threads. Seeds anatropous, 

 small, without albumen. Mostly herbs, with opposite or alternate leaves. Stip- 

 ules none or glandular. 



* Parts of the flower in fours or more numerous. 

 +- Fruit a many-seeded pod, usually loculicidal. 



H- Calyx-limb (divided to the summit of the ovary) persistent. 



1. Jussiaea. Petals 4-6. Stamens twice as many. Capsule elongated, 4-6-celled. 



2. Ludvigia. Petals 4 or none. Stamens 4. Capsule short. 



H- -H- Calyx-tube or deeply cleft limb deciduous from the summit of the capsule; petals 4; 



stamens 8. 



3. Epilobium. Seeds silky-tufted. Flowers (in ours) not yellow. Lower leaves often opposite. 



4. Oenothera. Seeds not tufted. Flowers mostly yellow. Leaves alternate. 



+- +- Fruit dry and indehiscent, 1-4-seeded. 

 H- Terrestrial ; leaves alternate ; stamens 6-8. 



5. Gaura. Calyx-tube obconical. Filaments appendaged at base. 



6. Stenosiphon. Calyx-tube filiform. Filaments (8) not appendaged. 



H- -H- Aquatic ; leaves opposite or whorled ; stamens 4. 



7. Trapa. Calyx-tube short. Filaments unappendaged. Fruit large, coriaceous, turbinate. 



* * Parts of the flower in twos ; leaves opposite. 



8. Circaea. Petals 2, obcordate or 2-lobed. Stamens 2. Fruit 1-2-seeded, bristly. 



1. JUSSIAEA L. PRIMROSE-WILLOW 



Calyx-tube elongated, not at all prolonged beyond the ovary ; the lobes 4-6, 

 herbaceous and persistent. Herbs (ours glabrous perennials), with mostly 

 entire and alternate leaves, and axillary yellow flowers in summer. (Dedicated 

 to Bernard de Jussieu, the founder of the Natural System of Botany.) 



1. J. decurrens (Walt.) DC. Stem erect, 3-6 dm. high, winged by the decur- 

 rent lanceolate leaves ; calyx-lobes 4, as long as the petals ; capsule cylindric- 

 club-shaped, wing-angled ; seeds in several rows in each cell. Wet places, 

 " Md." and Va. to Fla.; s. 111. and Mo. to La. and Tex. 



2. J. diffusa Forsk. Stem creeping, or floating and rooting ; leaves oblong, 

 tapering into a slender petiole ; flowers large, long-peduncled ; calyx-lobes and 

 obovate petals 5; pod woody, cylindrical, with a tapering base ; seeds quadrate, 

 in 1 row in each cell, adherent to the spongy endocarp. (J. repens of auth., 

 probably not of L.) In water or on muddy banks, Ky. and 111. to e. Kan., and 

 southw. 



2. LUDVfGIA L. FALSE LOOSE STRIFE 



Calyx-tube not at all prolonged beyond the ovary ; the lobes 4, usually per- 

 sistent. Capsule short or cylindrical, many-seeded. Perennial herbs, with 

 axillary (rarely capitate) flowers through summer and autumn. (Named ior 

 C. G. Ludwig, Professor of Botany at Leipsic, contemporary with Linnaeus.) 



