Dec, 1921] 
LEVINE — STUDIES ON PLANT CANCERS 
The average weight of the entire plants when fresh is 12.06 g. The 
average dry weight is 1.26 g. The uninoculated plants grown in plot "E," 
that is, in fertilized soil, attained an average weight of 30.96 g. with a dry 
weight of 2.64 g. (columns 5 and 6). The difference in the weights of the 
normal plants can be interpreted only as due to differences in the amounts 
of available food in the soil. 
The uninoculated plants in both plots were, as noted, scattered among 
those that had been inoculated. The average weight of the inoculated 
plants grown in unfertilized soil (plot "SW") is less than that of the healthy 
plants (see table 2, columns 3 and 4). This difference in favor of the normal 
plant indicates that the presence of the parasite in these cases has lowered 
the total growth (tissue-producing capacity) of the plant. 
A slight variation in the number and size of the leaves affects the total 
weights of the plants, yet the beet roots of the same variety bearing crown 
galls are always larger and weigh more than the normal roots grown under 
similar conditions. The marked difference in weight between the inoculated 
plants grown in plot "E" (fertilized soil, see table 2, columns 7 and 8) and 
the inoculated plants grown in plot "SW" is of considerable interest and 
not only indicates a difference in the nutritive conditions of the plants but 
confirms the data already obtained for these plants when, grown in pots, 
and also supports the contention that the healthy plant responds to the 
influence of an invading organism more vigorously than does the poorly 
nourished or less robust plant. 
These results further support the view maintained by many plant and 
animal pathologists that the response to an invading organism is greatest 
and that the parasite is most favored when the necessary metabolic proc- 
esses of the host are satisfied. 
The Weight of the Crown Gall Compared with the Weight of 
THE Plant 
I have further studied the weight of the crown-gall tumors from both 
the large and the small beets. The varieties used were Early Model, 
Egyptian Early, and Giant Mangel W^urzel. The plants in this experiment 
were grown under the most favorable conditions. When the tap roots had 
developed they were inoculated with Bacterium tumefaciens on August 4, 5, 
and 6, 1920, in the manner described above and were harvested October 15, 
1920. An equally large number of plants among the inoculated ones were 
left to serve as controls. Figure 8 represents a portion of plot "W" in 
which the Giant Mangel Wurzel was growing. 
For convenience, the crown gall was considered as that part of the root 
which could be separated from it by a stroke of the knife, continuous with 
the normal contour of the root. It is readily seen that this does not remove 
all the crown gall, for the neoplasia in the plant also invades the normal 
tissues, as Levin and Levine (1920) have shown for other plants, so that 
