Hickory (from Powhatan) is a type of tree, comprising the genus Carya ( "nut"). The genus includes 17–19 species of deciduous trees with pinnately compound leaves and large nuts. Five or six species are native to China, Indochina, and India (State of Assam), as many as 12 are native to the United States, four are found in Mexico, and two to four are from Canada. Hickory flowers are small, yellow-green catkins produced in spring. They are wind-pollinated and self-incompatible. The fruit is a globose or oval nut, long and diameter, enclosed in a four-valved husk, which splits open at maturity. The nut shell is thick and bony in most species, and thin in a few, notably C. illinoinensis; it is divided into two halves, which split apart when the seed germinates.