64 BOTANICAL GAZETTE [JULY 
The “peculiar form” and the ‘‘ particular location,” upon which 
PENHALLOW laid special stress, are readily understood when their 
origin is appreciated. The resin is produced in the parenchyma 
as a product, or more likely as a by-product, of the metabolic 
activity of those cells. The cavities of the adjacent tracheids 
become reservoirs for such portions of the resin as are excreted. 
Such excretions may retain the form of globules, or extend across 
the cavity and assume the form of thick or thin plates, or when the 
quantity is large nearly fill the cell. 
The writer does not consider the ‘“‘Cordaitales’’ (Araucarians) 
peculiar among the gymnosperms with respect to the form of the 
resin masses and their location. The same form and location 
obtain in Pinus albicaulis, not sporadically, but as a constant 
feature of the heartwood. Similar deposits have also been noted 
occasionally in the tracheids of P. resinosa, Picea sitchensis, and 
in abnormal sapwood of Pinus ponderosa, while globules of resin 
have been observed on the outside of the pit membranes of ray 
parenchyma cells in P. Strobus. These instances, taken in connec- 
tion with PENHALLOW’s note of the occurrence of resin plates in 
P. parviflora and in two species of Abies, lead the writer to believe 
that. they probably occur sporadically in many other representa- 
tives of the Coniferae. The writer has also noted tracheids in P. 
albicaulis with resin globules at several lateral pits connecting with 
the secondary epithelial cells of a vertical resin duct, showing that 
resinous tracheids in some instances may be independent of the 
rays. 
The association of the resin plates with special constriction of 
the tracheid cavity, as noted by PENHALLOw and figured by him 
for Dammara australis, appears to the writer to be without special 
significance. This constriction is due to increase in thickening 
of the tracheid walls where in contact with the rays, and has been 
observed by the writer as a common feature of the woods of various 
genera of the Coniferae, especially in the thick-walled cells formed 
late in the season. Such increase is presumably due to greater 
nutrition at that portion, and in most species is not in connection 
with resin plates, while the resin masses also occur where there are 
no such constrictions. 
