Hasseltia is a 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...

 of flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

s in the willow

Willow

Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...

 family, Salicaceae

Salicaceae

Salicaceae are a family of flowering plants. Recent genetic studies summarized by the Angiosperm Phylogeny Group has greatly expanded the circumscription of the family to contain 55 genera....

. It contains four 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...

 of small to medium-sized trees native to the neotropics, ranging from Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 south to Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 and Bolivia

Bolivia

Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...

.

Hasseltia is unique among Salicaceae in that the species have pseudo-axile placentation

Placentation

In biology, placentation refers to the formation, type and structure, or arrangement of placentas. The function of placentation is to transfer nutrients from maternal tissue to a growing embryo...

, compound umbel

Umbel

An umbel is an inflorescence which consists of a number of short flower stalks which are equal in length and spread from a common point, somewhat like umbrella ribs....

late inflorescence

Inflorescence

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

s, and a pair of glands embedded in the base of the leaf blades. Formerly placed in the heterogeneous family Flacourtiaceae

Flacourtiaceae

Flacourtiaceae is a defunct family of flowering plants whose former members have been scattered to various other families, mostly to Achariaceae, Samydaceae, and Salicaceae. It was so vaguely defined that hardly anything seemed out of place there and it became a dumping ground for odd and anomalous...

, Hasseltia is now classified in Salicaceae, along with close relatives Pleuranthodendron and Macrothumia, with which they are commonly confused.