Quassia is a flora genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 in the family

Family

In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...

 Simaroubaceae

Simaroubaceae

The Simaroubaceae is a small, mostly tropical, family in the order Sapindales. In recent decades it has been subject to much taxonomic debate, with several small families being split off...

. Its size is disputed; some botanists treat it as consisting of only one species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, Quassia amara

Quassia amara

Quassia amara is a species in the genus Quassia, with some botanists treating it as the sole species in the genus. It is a shrub or rarely a small tree, growing to 3 m tall , native to Brazil. The leaves are compound and alternate, 15-25 cm long, and pinnate with 3-5 leaflets, the leaf rachis being...

from tropical South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

, while others treat it in a wide circumscription as a pantropical

Pantropical

In biogeography, a pantropical distribution one which covers tropical regions of all of the major continents, i.e. in Africa, in Asia and in the Americas. Examples include the plant genera Acacia and Bacopa....

 genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 containing up to 40 species of tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s and shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

s. The genus was named after a Surinam slave Graman Quasi in the eighteenth century. He discovered the medicinal properties of the of the bark of Quassia amara

Quassia amara

Quassia amara is a species in the genus Quassia, with some botanists treating it as the sole species in the genus. It is a shrub or rarely a small tree, growing to 3 m tall , native to Brazil. The leaves are compound and alternate, 15-25 cm long, and pinnate with 3-5 leaflets, the leaf rachis being...

.

Broader treatments of the genus include the following and other species:

• Quassia africana
• Quassia amara
  Quassia amara
  Quassia amara is a species in the genus Quassia, with some botanists treating it as the sole species in the genus. It is a shrub or rarely a small tree, growing to 3 m tall , native to Brazil. The leaves are compound and alternate, 15-25 cm long, and pinnate with 3-5 leaflets, the leaf rachis being...
  
  
• Quassia bidwillii
• Quassia indica
• Quassia sp. 'Moonee Creek'
  Quassia sp. 'Moonee Creek'
  Quassia sp. 'Moonee Creek the Moonee Quassia is a shrub found in north eastern New South Wales, Australia. A rare plant, listed as endangered by extinction. However, it has yet to be formally named....
  
  - Australia
• Quassia sp. 'Mount Nardi'
  Quassia sp. 'Mount Nardi'
  Quassia sp. Mount Nardi is a plant found in north eastern New South Wales, Australia. An uncommon to rare plant, yet to be formally named. The original specimen was collected at Mount Nardi, not far from Nimbin....
  
  - Australia
• Quassia undulata

It is the source of the "quassinoids" quassin

Quassin

Quassin is a white bitter, crystalline substance extracted from the quassia tree. It is one of the most bitter substances found in nature with a bitter threshold of 0.08 ppm and it is 50 times more bitter than quinine....

 and neo-quassin.