DEVELOPMENT OF FORMS OF THE DISEASE. Dat 
numerical series, was dug each year for three years. Table X, in the 
appendix, gives the combined results of the experiment. 
The results of the experiment were in favor of the use of American 
seed for growing seedlings, since there was an increase of 4.9 per cent 
of crown-gall on the trees on roots grown from French seed, and, on 
the other hand, an increase of 1.3 per cent of hairy-root on trees grown 
from roots from American seed. If we combine the number of trees 
diseased both by crown-gall and hairy-root, there will be found an 
increase of 3.6 per cent of disease, due to the use of French seed. 
This difference is further accentuated by the number of trees grown 
from the same number of grafts on the roots from American seed, 2,255 
as compared to 1,802 on roots from French seed, or a gain of 25.1 per 
cent in favor of the use of the former. The experiment proves that 
the assumption that the use of American seed in growing seedlings 
tends to increase the development of crown-gall is erroneous and it 
indicates a superiority in seedlings from American seed. 
The use of seedlings from old nursery districts for making root grafts 
may not increase the development of the disease.—It has been asserted 
by some growers of nursery stock that seedlings purchased from 
regions where they had been grown year after year, and especially 
from Kansas, developed more crown-gall than those grown in new 
regions in soil where nursery stock had not been previously grown. 
To test the matter, two lots of grafts were made from the same stock 
of scions, including the following varieties: Yellow Transparent, 
Baldwin, Winesap, Maiden Blush, and Missouri. One set was made 
on seedling roots grown from French apple seed in the Kansas River 
valley, near Topeka, Kans., on soil subject to inundation from the 
river and overflow from neighboring nurseries and on which nursery 
stock had been previously grown; the other set was from another 
stock of seedlings grown from the same stock of seed by the same 
nursery company in a new locality near Lincoln, Nebr., on soil which 
had been cultivated in field crops for a number of years and on which 
nursery stock had never been grown. This set contained half as 
many root grafts.as the former. The grafts were made, planted, 
and grown with the same care as in all of the experiments. They 
were grown on cooperative plats 1 to 8, and a definite proportion, 
selected in a numerical series in each row, was dug each year at the 
ages of 1, 2, and 3 years. Table XI, in the appendix, gives in a 
condensed form the results of the experiment. 
In giving the results of this experiment it must be noted that the 
conditions under which the seedlings for the experiment were grown 
were not quite comparable for two reasons: The localities where they 
were grown (Kansas and Nebraska) varied in latitude, and the soil 
conditions were not quite the same, since these seedlings were grown 
186 
