Oct. 13, 1923 
A New Tumor of the Apricot 
5i 
area represents xylem parenchyma and tracheal tubes which disintegrated 
and became filled with gum. The earlier stages of the disease are illus¬ 
trated by the tissue bordering the lesion. Note the flat, narrow cells at 
A, evidently in a state of very rapid multiplication; note, also, the cells 
about B, which, like the affected cells of the phloem parenchyma, take 
the stain less deeply than the cells of the surrounding healthy tissue, 
have thinner cell walls, and are more irregular in shape—apparently 
undergoing a process of gelatinization similar to that through which the 
diseased phloem tissue passes in the course of its gummous degeneration. 
The smaller lesion in the upper left hand comer brings out the same 
facts. Gummous lesions in the wood have also been found involving wood 
fibers and pitted ducts. In these cases there was no multiplication of 
these elements, but merely a gummous breaking down. 
There are thus found in this gall of the Moorpark apricot the phenome¬ 
non of gummosis on the one hand, and hyperplasia—that is, abnormal 
and excessive cell division—on the other. No true hypertrophy, in the 
narrow pathological sense of the term—that is, an abnormal increase in 
the size of individual cells—has been observed. 
PROBABLE COURSE OF THE DISEASE: CONCLUSIONS 
In view of the fact that gummous lesions exist in the bast at a distance 
of from 1 to 2 inches beyond the gall, it seems probable that the first 
stage of the gall consists in a gummosis of portions of phloem tissue. The 
outlying region of the phloem just below the periderm is the first to become 
affected. The gummous lesions may later extend deeper into the 
phloem and occasionally cross the cambium to enter the wood. 
The cork cambium, in the meanwhile, receives a stimulus for abnormal 
cell division. As a result, cork strands diverge to enter the affected area, 
in what may be interpreted as an attempt to isolate the lesions or heal 
them over. 
In order to account for the large amount of phloem tissue involved in 
the tumor, as well as for the general increase in wood in the region 
underlying it, it must be assumed that the disease is accompanied by a 
general acceleration of cambial activity. The occasional proliferation of 
cells bordering the gum pockets is of very minor importance in this 
connection, and can not possibly be held to account for the large swellings 
produced. 
By replacing the phloem tissue as fast as it is destroyed, or nearly so, 
the cambium enables the tree to withstand the effects of the disease for 
long periods of time. 
The effect of the disease is to be looked for in a constant loss of indis¬ 
pensable tissue, which must be replaced in order that the tree may escape 
the danger of being ringed. When the cambium fails to replace the 
phloem as fast as it is destroyed, the disease is naturally aggravated, 
for such a condition results in interference with the translocation of 
manufactured food which must be carried through this tissue. 
EXPERIMENTAL DATA 
The general features of the histology of the galls were studied from 
wood-microtome sections. Recently formed tissue from the edges of 
the galls was sectioned fresh or after soaking in water. Where the 
material was permeated with gum, as is very often the case, it was soaked 
