FRANKINCENSE. 281 
studded by a series of horizontal excrescences or oblong elevations 
in the cortical covering, of a pale or yellowish brown hue, ap- 
pearing in dense parallel but disconnected strata, a quarter of an 
inch or more apart, and varying from one sixth to one inch n 
length and about one or two lines in breadth. Being of a lighter 
tint than the surrounding portions they are distinctly perceptible, 
and answer as a diagnostic peculiarity to identify the lesser shoots. 
As the tree approaches maturity, these elevated projections pro- 
portionately diminish, and the cortex, while partially retaining its 
smoothness, becomes traced by irregular patches of white or grey. 
In the course of time these patches enlarge to such an extent as to 
embrace in many instances the entire surface of the exterior. The 
inner cortical layers in plants of an immature development 
present a peculiar fibrous character, are delicately organized, and 
may be peeled off in smooth ribbon-like layers, which cannot be 
effected in the older specimens. 
The leaves are bi-pinnate, of a pale green pervaded by a greyish 
tint that also characterizes the trunk. In the younger productions 
they are of larger development, but the pinne are less numerous 
than in those of a later growth. 
The gum, when a natural exudation, mostly appears in a liquid 
state, of a white or pale straw-colour, in some seasons oozing so 
copiously from the branches that the ground and shrubs beneath 
are from successive excretions thickly covered with white spots. 
This effusion, however, does not occur so abundantly from the 
cortex, and when so produced appears in thin and shallow layers, 
that mark their course by whitish streaks which, after their exsic- 
cation on the trunk, present all the aspects of a saline efflorescence. 
The frankincense-tree is subject to the attack of a certain insect 
termed by the natives Tumbo, which deeply perforates the bark in 
various directions. Its progress is attended by long and sinuous 
passages, the woody débris from which is ejected externally by a 
circular orifice about an inch in diameter. In the course of a few 
days the gummy liquid issues largely from this aperture, blended 
with minute ligneous particles, which in their transit through these 
excavations acquire a ruddy or brown tint , by degrees accumulating 
in small masses and falling to the earth. In this state they become 
converted into dark brown fragments after a short interval, and 
are then gathered by the negro women and children who resort to 
the woods with the express purpose of collecting them. Another 
