70 BULLETIN 1380, U. S. DEPARTMENT OF AGRICULTURE 
CORTEX NODULES 
In addition to the abnormalities formed by the callus around 
tapping wounds and preventitious and adventitious structures, an- 
other nodule formation, which has an entirely different origin, not 
infrequently occurs in the cortex of badly tapped trees. These are 
cortex nodules, which are said to be very common on Hevea in the 
Orient and are associated with trees which have been badly tapped 
or tapped for a long time, or they may follow brown-bast and other 
cankers. 
Kuyper has reported and figured such nodules on Hevea in Dutch 
Guiana. Concerning their occurrence on Hevea in the Amazon 
Valley Akers states that he looked carefully for signs of these 
nodules, but found no trace of them, in spite of the fact that the 
cambium is damaged at every stroke of the collector's ax. He con- 
sidered that Hevea since its introduction in the Orient had under- 
gone a constitutional change favorable to the production of nodules. 
In his second work, however, he refers to these nodules on old 
trees and quotes suggestions in explanation of their origin. 
It is not unlikely that considerable confusion has resulted from a 
misinterpretation of the cause and origin of the various t} r pes of 
nodules on Hevea and that what has been considered a nodule in the 
usual sense is nothing more than a callous formation or a growth 
arising from new or arrested buds. 
Occasionally on old trees which have been badly damaged in tap- 
ping, cortex nodules are not uncommon, but care must be used in the 
diagnosis of certain of the forms. The nodules may be observed in 
all stages of development. They may appear singly, in clusters, or 
may take the form of vertical elongated swellings or ridges. 
The first indication of these nodules is a slight swelling. If the 
outer bark is removed a small mass of wood is found embedded in 
the cortex without connection with the wood of the stem. The 
nodule increases in size by the multiplication of the cells of its own 
cambium, which puts down concentric layers of wood until the 
nodule attains considerable size. Later, with increased growth, the 
wood of the nodule fuses with that of the trunk, and a permanent 
protuberance or swelling is formed. Sometimes before the nodules 
become attached to the wood they may be exfoliated with the dead 
bark scales, or they may project and be so lightly attached that they 
may be removed with a slight pressure. If they become attached 
and at the same time project, the cortex frequently becomes disor- 
ganized at the outer surface and an open cuplike cavity is formed 
(PL III, D). 
The initial stages of the nodules vary greatly in shape. They 
may be spherical, elongated, or more or less cylindrical, or they 
may consist of fiat plates which are developed either by the lateral 
fusion of a number of small spherical nodules (PL XXX, B) or 
by growth in the form of anastomosing wood fibers. The openings 
in the fibers through which the cambium extends eventually are 
closed up, leaving slight depressions on the surface of the plate 
(PL XXX, B). The shape of the initial nodule apparently de- 
termines the type of burl or swelling produced and does not appre- 
ciably change in later development. A single spherical nodule con- 
tinues its development until it may form a protuberance 1 to 2 
