Artemisia annua
Artemisia annua, also known as Sweet Wormwood, Sweet Annie, Sweet Sagewort or Annual Wormwood (Template:Zh-cp), is a common type of wormwood that grows throughout the world. It has fern-like leaves, bright yellow flowers, and a camphor-like scent.  It averages about 2 m tall and has a single stem, alternating branches, and alternating leaves which range 2.5-5cm in length.  It is cross-pollinated by the wind or insects.  It is a diploid organism with chromosome number, 2n=36.
Sweet Wormwood was used by Chinese herbalists in ancient times to treat fever, but had fallen out of common use, to be rediscovered in 1970 when the Chinese Handbook of Prescriptions for Emergency Treatments (340 AD) was found.  This pharmacopeia contained recipes for a tea from dried leaves, prescribed for fevers (not specifically malaria).  In 1971, scientists demonstrated that the plant extracts had antimalarial activity in primate models, and in 1972 the active ingredient, artemisinin (formerly referred to as arteannuin), was isolated and its chemical structure described.  Artemisinin may be extracted using a low boiling point solvent such as diethylether and is found in the glandular trichomes of the leaves, stems, and inflorescences, and it is concentrated in the upper portions of plant within new growth.  Artemisinin itself is a sesquiterpene lactone with an endoperoxide bridge and has been produced semi-synthetically as an antimalarial that is commonly used in tropical nations which can afford it, preferentially as part of a combination-cocktail with other antimalarials in order to prevent the development of parasite resistance.
The question as to whether tea made from A. annua should be used to treat malaria is contentious.  Those against argue that artemesinin is not soluble in water and only very low concentrations are achieved that are insufficient to treatment malaria reliably. Those for argue that Artemisia annua contains a cocktail of anti-malarial substances, and insist that clinical trials be conducted to demonstrate scientifically that artemisia tea is just as effective in treating malaria as it appears to be where it is regularly used. If it is proven, then it will present itself as a cheaper alternative to commercial pharmaceuticals, and will enable health dispensaries in the Tropics to be much more self-reliant in their malaria treatment. James Duke and Mike Benge et al, Chemical and Engineering News, Letters, Vol 83, No 18, pp4-5. More detailed findings can be found in www.anamed.net 
The plant has also been shown to have anti-cancer properties. It is said to have the ability to be selectively toxic to breast cancer cells  and some form of prostate cancer, there have been exciting preclinical results against leukemia , and other cancer cells.
The proposed mechanism of action of artemisinin involves cleavage of endoperoxide bridges by iron producing all sorts of free radicals (hypervalent iron-oxo species, epoxides, aldehydes, and dicarbonyl compounds) which damage biological macromolecules causing the parasite oxidative stress. Malaria is caused by the Apicomplexan, Plasmodium falciparum, which largely resides in red blood cells and itself contains iron-rich heme-groups (in the from of haemozoin). Cancer cells also tend to have higher iron concentrations than normal cells because of their rapid growth rate.

# Other uses
In modern-day central China, specifically Hubei Province the stems of this wormwood are used as food in a salad-like form.  The final product, literally termed "cold-mixed wormwood" is a slightly bitter salad with strong acid overtones from the spiced rice vinegar used as a marinade.  It is considered a delicacy and is typically more expensive to buy than meat.