Oct 13, 1923 
A New Tumor of the Apricot 
47 
1. The wood in the region underlying the tumor growth is somewhat 
hypertrophied, as is seen from a comparison of the diameter of the wood 
in this region with its diameter at a point beyond the constrictions 
referred to above. 
2. The line of demarcation between the wood and the bast is sharp. 
The wood does not extend into the region which constitutes the excres¬ 
cence, properly speaking. This line of demarcation, which is perfectly 
definite in the specimen shown on Plate 3, is somewhat vague in the one 
in Plate 4, A, showing a longitudinal section of an affected root; but in 
neither case is the wood found mingled in the tissues composing the 
tumor. 
This distinctive feature of the disease is more clearly brought out when 
the views of the longitudinal sections shown on Plates 3 and 4, A, are con¬ 
trasted with the view in Plate 4, B, showing a limb with an “ aerial crown- 
gall” on it in longitudinal section. In the case of the gall caused by Bac¬ 
terium tumefaciens it is evident that the tumor consists largely of wood 
tissue. In fact, the bark has not increased much in thickness, while the 
wood has been greatly hypertrophied. In the apricot disease, however, 
the excrescence consists primarily of tissues lying outside of the cambium 
line; the wood, which is but slightly hypertrophied, having failed to 
extend into the tumor. This apricot disease is therefore a bark excres¬ 
cence, while crowngall may be termed a woody tumor. 
This feature of tie apricot disease has been found to be constant. It 
is considered a reliable criterion, by means of which the disease may be 
readily differentiated from crowngall, with which it is sometimes confused. 
To resume the description of the anatomy of the apricot gall: It will be 
noted from Plates 3 and 4, A, that the wood tissue shows lesions. These 
consist of irregularly shaped gum pockets, having a dark chestnut color. 
In young, actively growing galls they have been found to extend from the 
cambium line into the wood to a distance of 1 to 2 mm. Plate 4, A, 
representing a young gall on a root, shows the wood riddled by these 
pockets along the cambium line. This, however, is an extreme case 
which never occurs in the aerial galls. It seems quite obvious that the 
disease never works its way deeply into the wood. The fact that the 
gum in the pockets in the interior of the wood is dry, indicating that the 
lesions are probably stationary, coupled with the observation that they 
are often found along the yearly rings of growth, leaves little doubt that 
these lesions were formed through the extension of lesions from the 
phloem into the adjacent wood, and have subsequently been separated 
from the phloem by the interposition of successive layers of wood tissue 
in the course of the tree's growth. 
Scattered through the bast are large numbers of small gum pockets, 
varying in shape and outline. They range from microscopic dimensions 
to several millimeters in diameter, often forming confluent lakes, and are 
packed with gum and disintegrating tissue of a fight bay to fight chestnut 
color. Although moist, the contents of these pockets are not watery, but 
rather firm and will fall out bodily on pressure, leaving empty holes behind. 
Such gum pockets are very abundant in the bast region immediately 
below the excrescence, and have been found in lesser quantities through¬ 
out the bast at distances of 1 to 2 inches beyond the visible swelling. 
The gum becomes more and more abundant towards the exterior in the 
direction of the cork. The bast is found grading into a region throughly 
permeated with gum. This region corresponds in its position to that of 
the normal cork. It is, in fact, continuous with the normal cork beyond 
