Pinus branch showing needles
arranged in fascicles.

Pinus L., with 110 to 115 species is the largest genus of Pinaceae (Price et al. 1998; Farjon 2005). Species diversity is highest in Mexico, East Asia, the western United States (principally California), and the southeastern United States.

The monophyly of Pinus is well supported by traditional synapomorphies including a specialized shoot dimorphism that gives rise to needles arranged in fascicles, and woody ovulate cone scales with a specialized umbo and apophysis complex resulting from maturation over two (or three) growing seasons. The genus is divided into two subgenera that are separated by the presence of either one vascular bundle in the leaf (subgenus Strobus) or two (subgenus Pinus).

Leaf cross section

Pinus pseudostrobus, subsection Ponderosae).
Prepared by Calixto Leon Gomez.

Cone axis cross section

Prepared by Calixto Leon Gomez.