Botanical name: 

The whole plant of Oenothera biennis, Linné (Nat. Ord. Onagraceae). A common plant in waste places in the United States. Dose, 5 to 60 grains.
Common Names: Evening Primrose, Tree Primrose.

Principal Constituents.—Tannin and an abundance of mucilage; also potassium nitrate and aenotherin, a mixture of substances not well determined.
Preparation.—Fluidextractum Oenothera, Fluidextract of Oenothera. Dose, 5 to 60 drops.

Specific Indications.—Dirty, sallow, full and expressionless skin and tongue, the latter being unnaturally large; face dull and apathetic, and patient gloomy and despondent; dyspepsia with vomiting of food, gastric distress, and frequent desire to urinate.

Action and Therapy.—Oenothera is but little used, but has been suggested by Scudder as useful in gastro-hepato-splenic disorders, with the symptoms named above. Webster believes it may prevent ulceration of Peyer's patches. It is probably of some value in gastric distress following meals, with the gloomy and melancholic state of mind which frequently accompanies dyspeptic conditions. It has also been advised in pelvic fullness and torpor in women. Undoubtedly it does relieve the desire to frequently pass urine and has been used after gonorrhea for this purpose.

The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.