58 BULLETIN 1380, U. S. DEPARTMENT OF AGRICULTURE 
black Hevea is classified as fina and that from the others as fraca 
(weak). There is considerable confusion in the application of these 
color terms. In one part of the valley the terms refer to the outer 
color of the bark; in another they apply to the color of the tissues 
of the cortex. To eastern investigators who have been more accus- 
tomed to the light-colored cortex it must be a matter of surprise to 
find that most of the trees growing on dry land (terra firma) have a 
reddish colored cortex tinged with brown or purple. Such colors 
when known only in association with brown-bast would lead to con- 
fusion until the varieties are learned. In the lower Amazon region, 
where many trees grow on swampy land or where the land is subject 
to frequent inundations, the variety with light-colored cortex pre- 
dominates. It was from this variety with a few exceptions that the 
seeds were obtained to establish the plantations in the Orient. 
From the standpoint of preliminary observations on the presence 
of brown-bast in the Amazon Valley the normal color of the cortex 
should be held in mind. In the white variety the color changes 
induced by the disease are readily apparent. So far as the investi- 
gations were carried, the symptoms of brown-bast were observed 
only in the white variety, which leads to the conjecture that this 
form may be more susceptible to the disease. On a living Hevea 
stump with the red-colored cortex rough bark scales were apparent. 
These when removed showed a watery, sodden appearance beneath, 
without color change. The tissues thus exposed were laticiferous. 
Further study is necessary to determine the reactions in cortex of 
this color. 
WOUNDS 
Numerous kinds of wounds found on Hevea may be roughly 
divided into two groups : Those which result from the natural 
processes of growth, frequently intensified by adverse conditions, 
and those resulting from external causes. 
Before the different kinds of wounds found on Hevea in the 
Amazon Valley and their effect on the health of the tree are described 
it seems desirable to discuss the natural processes by which the tree 
attempts to restore its injured parts. 
The tissue concerned in the protection of the living cells of young 
twigs and stems is a thin layer of epidermis, the periderm. When 
the periderm ruptures through the increased growth of the parts 
beneath, its cells or those of the phellogen (cork cambium), situated 
beneath the periderm, divide tangentially, and a new protective 
covering is immediately formed over the living tissues. The re- 
newal of this protective layer by the cork cambium on its inner 
surface and the cutting off of cells which soon lose their power of 
division on its outer surface are constant processes and result in 
the formation of an outer layer of dead cork or, as it is called, the 
bark. The entire structure is known as the cortex. The meriste- 
matic nature of the cork cambium beneath the outer dead bark is 
the mechanism which produces a protective layer when wounds are 
formed in the cortex. In such cases the protective layer is known 
as wound cork and may be very rapidly developed, especially at 
the edge of wounds which h'ave exposed and killed the true cambium. 
