cross section: Pinus needle magnification: 400x

Pinus needles may be circular, semicircular or triangular in cross section and are structurally adapted to tolerate xeric stress and freezing.

A single layered epidermis of lignified cells is covered by a heavy waxy cuticle. Numerous sunken stomata are scattered over the entire epidermal surface. They are bounded by pairs of subsidiary cells, and open internally to a substomatal cavity and externally to a respiratory cavity or vestibule.

The underlying hypodermis consists of several layers of thick-walled sclerenchyma, particularly well-developed at ridges.

Deep to the hypodermis lies an undifferentiated photosynthetic mesophyll. Cells are distinctively lobed with infolded cell walls. They are filled with chloroplasts and starch grains that may be difficult to see because of an accumulation of dark staining tannins and resins. A few resin canals can be seen close to the hypodermal side of the mesophyll.