The number of radial resin ducts was significantly higher in slash pines than in loblolly, longleaf, or shortleaf. Average width of resin ducts was less in shortleaf than in the other three species. Flow rate of oleoresin was not correlated with size or number of resin ducts for any of the four species.
Hodges, John D.; Elam, William W.; Bluhm, Donald R. 1981. Influence of Resin Duct Size and Number on Oleoresin Flow in the Southern Pines. Res. Note SO-266. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 3 p.