COMMUNICABILITY OF THE DISEASE. yl 
trees the third year, with a tree digger. In digging the trees with 
spades those remaining were often wounded, and this alone should 
have led to an increase of disease. In this and in all of the other 
experiments mentioned in this bulletin conducted by the author he 
personally examined the root grafts when made, directed the planting 
and cultivation, saw every tree as it was dug, and noted in each case 
the condition of the roots. 
Increase of the disease due to poorly fitted root grafts.—In order to 
determine the relation of defective grafting to the increase of crown- 
gall in the nursery a number of experiments were conducted. Two 
series of whip or tongue root grafts were prepared from the same lots 
of scions and seedling roots. The varieties Gano, Wealthy, Red June, 
Martha, and Whitney were used. The root grafts of one series were 
carefully made, root and scion pieces of equal diameter being selected 
and smoothly fitted at the union (PI. IX, fig. 2, A). The second 
series consisted of similar grafts very poorly fitted in which either 
root and scion piece were of different diameters or the end of the 
one projected beyond the surface of the other (Pl. IX, fig. 2, OC 
and PD). 
These root grafts were planted in eight equal lots in experiments 
1, 2, and 3 in cooperative plats 1 to 8 (for description see p. 78). 
In experiment 1, four lots of grafts planted in cooperative plats 1 to 4, 
every third tree was dug at the end of one season, every second at the 
end of two years, and the remaining trees at the end of the third 
year. In experiment 2, two lots planted in cooperative plats 5 and 6, 
every other tree was dug at the end of the first season, and the remain- 
ing trees at the end of the second year. In experiment 3, two lots 
planted in cooperative plats 7 and §, all of the trees were dug at the age 
of 2 years. Table X XV, in the appendix, gives the results from each 
of the experiments. 
A smaller experiment, similarly prepared, in which a number of 
poorly fitted root grafts and twice as many carefully fitted grafts 
from the same stock of scions and seedlings were made, was conducted 
in eastern Missouri. The results of the experiment are as follows: 
Out of a total of 357 trees grown from the smoothly fitted root 
erafts, 7.8 per cent was diseased with crown-gall and 5.1 per cent 
with hairy-root; and out of a total of 217 trees grown from the poorly 
fitted root grafts, 17.5 per cent was diseased with crown-gall and 11.1 
per cent with hairy-root, or a saving of 15.7 per cent on trees of a 
marketable size due to smooth fitting. 
Briefly summarized, the results of these experiments are as follows: 
(1) Poorly fitted root grafts, as compared with carefully fitted 
ones, yielded an increased percentage of diseased trees both with 
crown-gall and with hairy-root. The increase of crown-gall in both 
186 
