CuticleA thick waxy covering on the outside of the needle.
EpidermisThe outer layer of cells, with very thick walls.
HypodermisThick-walled cells under the epidermis. They stiffen the needle.
Sunken stomaA pore that lies at the bottom of a pit.
MesophyllThe food-making tissue of the needle. Its cell walls fold inward.
Resin ductA canal lined by cells that make resin.
EndodermisA ring of cells around the central region.
Vascular bundleA strand of xylem and phloem. This needle has two.
Up close 4
Guard cellsThe two cells beside the pore, deep in the pit.
XylemThe water-carrying half of each bundle. It faces the flat side.
PhloemThe other half of each bundle. It faces the curved side.
Transfusion tissueTissue that fills the space around the bundles.
How this list was compiled: Every name checked on 2026-10-03 and kept only where two of these use it. (1) J. M. Coulter and C. J. Chamberlain, Morphology of Gymnosperms, 1910 (public domain), the leaf of the Pinaceae and figure 259, https://archive.org/details/morphologyofgymn00couluoft : the epidermis with strongly cutinized walls; the guard cells deeply sunken; hypodermal layers of sclerenchyma, to which the rigidity of the leaf is chiefly due; the mesophyll uniform throughout, with plate-like infoldings of the wall, and containing resin ducts; a distinct bundle sheath (endodermis) around the vascular region; two parallel vascular bundles with the xylem toward the flat face; the remaining tissue within the sheath is the transfusion tissue. The same figure and words stand in Coulter, Barnes and Cowles, A Textbook of Botany, 1910, which is counted with it. (2) A. Michavila and others, An immunohistochemical approach to cell wall polysaccharide specialization in maritime pine (Pinus pinaster) needles, Protoplasma, 2025, open access, https://doi.org/10.1007/s00709-025-02041-5 : a thick wax cuticle; epidermis and hypodermis; sunken stomata with guard cells; a mesophyll of cells with an infolded shape; resin ducts lined by epithelial cells; the endodermis surrounds the central cylinder; two collateral vascular bundles of xylem and phloem; transfusion tissue around the bundles, which moves water and solutes between the mesophyll and the bundles. (3) G. Haberlandt, Physiological Plant Anatomy, 1914 (public domain), https://archive.org/details/physiologicalpla00habeuoft : the thick-walled, cutinized epidermal cells of the leaf of Pinus; the folds or flanges of the green cells of a pine needle; resin ducts under the epidermis of the needle; transfusion tissue around the whole vascular strand in Pinus, inside a thick-walled sheath. (4) W. C. Stevens, Plant Anatomy, 1910 (public domain), https://archive.org/details/plantanatomyfrom00stev : the resin duct in a leaf of Pinus, a canal with a sheath of secreting cells. (5) Wikipedia, Pine, Resin canal and Vascular bundle, https://en.wikipedia.org/wiki/Pine : pines are sorted by the number of vascular bundles in the needle; resin canals are spaces surrounded by cells that secrete resin; in a leaf the xylem lies toward the upper side and the phloem toward the lower. (6) M. Sutherland, A Microscopical Study of the Structure of the Leaves of the Genus Pinus, Transactions and Proceedings of the Royal Society of New Zealand, volume 63, 1934, https://archive.org/details/transactions-and-proceedings-royal-society-new-zealand-63-517-568 : a glossary that defines the cuticle, epidermis, hypodermis, guard cells, mesophyll (the assimilating tissue, with infolded walls in pines), endodermis, phloem, transfusion tissue and the vascular bundle of xylem and phloem; in its descriptions of the needle of each pine, most have two vascular bundles and some have a single one. Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry; own work, nothing traced. Licence: own work
How it works
Pine needle cross section labeled from the outside in: cuticle, epidermis, hypodermis, mesophyll with resin ducts, endodermis and two vascular bundles. The second drawing enlarges one sunken stoma and the middle of the needle.
Read the full guide
The tough outside
A thick waxy cuticle covers an epidermis of thick-walled cells. Under it, the hypodermis stiffens the needle. Each stoma lies at the bottom of a pit, with its guard cells below the surface.
Inside the needle
The mesophyll is one uniform tissue, and its cell walls fold inward. Resin ducts run through it. The endodermis rings the central region, where two vascular bundles lie, xylem toward the flat face and phloem toward the curved face, with transfusion tissue around them.
Questions and answers
What are the parts of a pine needle in cross section?
From the outside in: cuticle, epidermis, hypodermis, mesophyll with resin ducts, and the endodermis around a central region that holds the vascular bundles and the transfusion tissue. Sunken stomata pierce the outer layers.
What is transfusion tissue in a pine needle?
The tissue that fills the space between the vascular bundles and the endodermis. It moves water and dissolved substances between the bundles and the mesophyll.
What does a resin duct look like in a pine needle?
A round canal ringed by cells that make resin. In a cross section the ducts show as holes in the mesophyll, each with a ring of cells around it.
What are sunken stomata?
Stomata that lie at the bottom of a pit, with the guard cells below the surface of the leaf. Botany texts list them, with a thick cuticle, among the features of plants of dry places.
How many vascular bundles does a pine needle have?
One or two, depending on the kind of pine; botanists use the number to sort pines into two groups. This drawing shows two, side by side inside the endodermis.