SIGNIFICANCE OF RESINOUS TRACHEIDS 
SAMUEL J. RECORD 
(WITH FIVE FIGURES) 
The occurrence of resinous tracheids in gymnosperms has been 
noted by PENHALLOW’ in the woods of certain species of Cordaites, 
Araucaria, Dammara, and a few representatives of the higher 
Coniferales, namely, Pinus albicaulis, P. parviflora, Abies Fraseri, 
and A. grandis. Such tracheids do not differ structurally from 
other tracheids, but are distinguished by their resinous contents. 
The resin within them is localized and usually extends across the 
cavity to form an imperforate septum or plate, which, in unstained 
sections, may give the cell the appearance of being structurally 
septate. 
PENHALLOW figures the common form of these plates in 
Dammara australis. Figs. 1-3 illustrate the resinous tracheids in 
the wood of Pinus albicaulis, showing the characteristic form of the 
resin masses (RPI) and their association with the medullary rays. 
The resinous contents of the latter are omitted in order not to 
obscure the structure. It will be noted that there is considerable 
difference in the thickness of these plates, which are invariably 
thinnest in the middle, and not infrequently ruptured there. By 
comparison with PENHALLOw’s drawings it will be seen that the 
location, form, and distribution of the resin masses in the two 
species are identical. 
The close association of the rays with the resin plates in the 
tracheids clearly indicates the origin of the resin, which in some 
cases can be seen in the form of globules on the outside of the pit 
membrane of the parenchyma cell. When enough has exuded to 
form contact with the opposite wall of the tracheid, the surface 
tension of the liquid and the attraction of the cell wall cause it to 
assume a double concave form like a drop of water in a small glass 
* PENHALLOW, D. P., A Manual of the North American gymnosperms. Boston: 
Ginn & Co. 1907 (pp. 53-58)- 
61] [Botanical Gazette, vol. 66 
