bers 
EFFECT OF THE DISEASE ON APPLE TREES. 35 
erative plats 1 and 2, in southwestern Iowa; plat 3, in eastern 
Nebraska; plat 4, in western Illinois; and plat 6, in eastern Kansas. 
In five of these sets of experiments, the results of which are given in 
Tables XV and XVI, in the appendix, a definite proportion of the 
trees, selected in a numerical series in the row, was dug at the age of 
1 year, and the remainder at the end of the following season. 
From Tables XV and XVI it will be seen that the average height of 
healthy trees in the experiments at the age of 1 and 2 years was 37.2 
and 56.4 inches, respectively, as compared with 33.5 and 51.3 inches 
for trees diseased with crown-gall and 34 and 53 inches for trees 
affected with hairy-root. In other words, galled trees were only 
ninety hundredths and ninety-one hundredths and hairy-rooted trees 
ninety-one hundredths and ninety-four hundredths as tall as healthy 
ones. A few measurements of root-grafted trees made at the end of 
three years indicate that approximately the same rate for each still 
held at the end of the third year’s growth. A few measurements 
were made of the diameter of healthy and diseased trees of some of 
the rows in each experiment, but time would not permit of the meas- 
urement of all. It was found that the ratio of the diameters was 
approximately the same as that of the heights, viz, almost 10 to 9.5 
for healthy and diseased root-grafted trees in the nursery. 
In conclusion it must be said that taken collectively the forms of 
crown-gall and of hairy-root do have a slightly stunting effect on 
root-grafted trees in the nursery during the first three years, and for 
that reason, at least, such trees are not equal to healthy ones for plant- 
ing in orchards. This conclusion as to hairy-root is given with the 
following modifying statements: 
(1) The effect of the simple form of hairy-root in stimulating root 
production in root grafts is described on a previous page. When 
cuttings are taken from trees diseased with the knots or the aerial 
form of hairy-root and planted or used as scions, root formation is 
more abundant than with healthy cuttings. Roots are thrown out 
readily, especially from the young knots, producing the woolly-knot 
form (PI. V, fig. 2, and Pl. VII, figs. 1 and 2). Such trees are some- 
times more vigorous growers for a time than healthy trees. The final 
effect is not yet known. 
(2) The abnormal root production of the woolly-knot form often 
stimulates the growth of grafted trees, and, as a result, such trees fre- 
quently become the largest in the row. This stimulation often con- 
tinues after the trees are planted in the orchard. The largest tree in 
experimental orchard 1 was diseased with woolly-knot (PI. IX, fig. 1). ° 
LITTLE OR NO EFFECT ON ORCHARD TREES SHOWN IN EXPERIMENTS. 
Experiments by others—Orchardists and nurserymen, as well as 
investigators, differ in their opinions as to the effect of crown-gall and 
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