OLEORESIN PRODUCTION. 5 
Longleaf pine as found in the southern United States of America 
is the species chiefly discussed and illustrated in the following pages 
as the typical producer of American naval stores. Botanically, it is 
classed in the division of the Spermatophyta, the subdivision of the 
Gymnospermae, the order Coniferales, and family Pinaceae. The 
structure of the wood, the principal subject of this research, as seen 
with the aid of the microscope in an end view or cross section made 
from a normal unturpentined specimen, is shown in Plates II, V, and 
VI. The yield of oleoresin, obtained when a tree is wounded, comes 
from the cells of the aggregates GP, Plate II, figures 3, 4, 5, and 
elsewhere. 
CAMBIUM. 
The cells of the wood and bark of the pine are formed by the 
division and differentiation of the cells of the cambium layer, which 
is situated between the bark and the wood (C, PL II, fig. 1). This 
layer is made up of thin-walled cells, which retain their power to 
divide and thus produce the new cells composing the yearly rings of 
bark and wood, respectively. 11 
ANNUAL RINGS. 
The layer of new wood formed each year on the outside of the 
woody core of a tree is known as an annual ring (AR, PI. II, figs. 1, 
2, 3, and 5.) In the pines in question it is conspicuously differen- 
tiated into two portions. The spring wood (SP) has thin-walled 
cells and large cavities, and forms early in the growing season. The 
summer wood (SM) has denser cell walls, and though it may begin 
to form as early as June, it generally develops in July, or, at the 
latest, August. The width of the annual ring and the amount and 
density of the summer wood formed are markedly influenced by tur- 
pentining, and serve as indicators of the effects of the various 
methods used. 
SAPWOOD AND HEARTWOOD. 
A varying number of the outermost annual rings of wood make 
up the sapwood. This is usually lighter in color than the heartwood, 
or central portion of the tree. The water solutions of the sap cir- 
culate through the sapwood, and it is in this region that the oleoresin 
exudes from certain cells (parenchyma) which are characteristically 
active. Each year a portion of the inner sapwood ceases to function 
and becomes dead heartwood ; as a result the thickness of heartwood 
increases with the tree's age, but that of the sapwood remains, with 
relatively small variations, approximately the same. The walls of 
u It is the cambium that tears when the wood is separated from the bark cylinder in 
making a willow whistle. 
87404°— 22 2 
