Turnera diffusa, Turnera aphrodisiaca
The leaf of this desert plant, found in North and Central America and Africa, contains alkaloids that directly stimulate the nerves and sex organs and increase circulation. Combined with its muscle relaxant properties, damiana is a genuine (if mild) aphrodisiac. It seems to work best when used over a period of several days.
Damiana also produces a euphoria like that produced by the THC in Marijuana for 1 to 1 1/2 hours. You can also place it within a brownie mix, as is done with marijuana. This cuts the bitter flavor, but not the effects (so far as I know - I haven't tried it, myself).
Additional uses of damiana are as a diuretic and laxative, as a stomach calmer, and as a general tonic. It's also useful for young women with irregular cycles or who have entered menopause or have other hormonal imbalances. Homeopathy suggests its use in people whose sexual problems are due to anxieties.
Damiana is legal in the United States, but like most herbs that have mind-influencing affects there have been attempts at legislation to prevent its sale in some states. Excessive long term use of this herb may be toxic to the liver, in a manner similar to alcohol, but as with alcohol this will take a lengthy amount of time and very heavy use of the herb.