A pinnate compound leaf has leaflets growing from a central rib stalk or axis of the leaf somewhat in the manner of feathers on an arrow. The four plant genera that most often have pinnate compound leaves are palms in the Arecaceae family of plants, cyads (Cycadaceae), some legumes (Fabaceae) and a few members of Grevillea (Proteaceae). Trees in the legume genus are rare; flowering plants in the Grevillea genus do not grow into trees.
The leaves of palm trees, called fronds, grow from a sheath at the base. The stalk or petiole tapers outward. The pinnate leaves growing from the sides of the stalk vary in length according to the species. Depending on the species, the size of the leaves growing from the palm trees stalk are as large as tens of feet or as small as a few inches. Examples of palm trees with pinnate compound leaves or fronds include the Cuban royal palm (Roystonea regia) also called the Florida royal palm, which is native to Florida, Mexico and the Caribbean, and the zamia palm (Macrozamia riedlei), native to western Australia.
There are some 100 species of Cycad, a genus of plants that look like palm trees. Some Cycads were first thought to be palm trees and some still bear the popular name of a palm trees. Instead of flowers and fruits, Cyads have cones, much like conifer trees. They are found in tropical regions around the world and in southern Florida. Examples of Cycads with pinnate compound leaves are the sago palm (Cycas revoluta), native to Japan, and the coontie (Zamia floridana), native to southern Florida.
Odd and Even
There are two main types of pinnate compound leaves. Some have an odd number of leaflets, made possible by a leaflet at the end. Others have an even number of leaflets. Trees with an odd number of pinnate compound leaves include the golden rain tree (Koelreuteria elegans) and the Brazilian pepper tree (Schinus terebinthifolius). Trees with an even number of pinnate compound leaves include the tamarind tree (Tamarindus indica) and the candle bush (Senna alata), a small, flowering tree with medicinal properties.
Pinnate compound leaves on a single stalk may be divided into even smaller leaflets. Trees with bi-pinnate compound leaves include the chinaberry (Melea azedarach), a species of mahogany, the royal Poinciana (Delonix regia), a legume, the jacaranda (Jacaranda spp), a small, flowering tree, and the mimosa tree (Albizzia julibrissin).
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