60 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE, 
eased. Growers of root-grafted trees will make no mistake if they 
insist on getting scions from strictly healthy trees, and they should 
grow their own healthy scions if possible. 
SELECTION OF HEALTHY SEEDLING ROOTS NECESSARY. 
The selection of healthy seedling trees from which roots are to be 
taken for root grafts is of prime importance to the grower. It has 
already been shown by experiment that the selection of roots from 
seedling trees diseased with hairy-root often results in the growth 
of a tree with diseased and deformed roots (Pl. VII, figs. 3 and 4), 
one which is unmarketable, even though in many cases it would no 
doubt develop into a profitable tree in the orchard. It is not profit- 
able to grow diseased trees or to be the distributor of diseased stock. 
It has also been shown by experiment that it is not best to use 
the apparently healthy portion of a seedling root which bears a soft 
gall. The use of such stock will certainly result in an increase of 
this form of disease and can not be profitable. 
Finally, it must be said to growers of seedling apple trees that 
when the seedlings are dug, all rough, warty, hairy, or tufted seed- 
lings should be rejected and destroyed (PI. III, fig. 1, and Pl. IX, fig. 
2,G@and H). Asa matter of precaution, they should not be tied up 
with healthy seedlings. Nurserymen purchasing seedlings for mak- 
ing root grafts should insist on this. 
CAREFUL FITTING OF ROOT GRAFTS NECESSARY. 
The influence of a projecting scion in the formation of excessive 
callus and the liability of such callus through infection to develop into 
crown-gall has already been discussed. It will pay nurserymen to put 
a premium on neat, close-fitting tongue grafts made at a reasonably 
rapid rate rather than to encourage the rapid manufacture of a 
poorly-fitted graft with the scion projecting at the union or with one 
made too blunt at the lower end, such as are shown in Plate IX, 
figure 2, C and D. The best results with the least amount of dis- 
ease will be secured by the use of No. 1 unbranched seedling roots 
upon which there have been closely and smoothly fitted scions of 
equal diameter, properly wrapped. The stress of competition in 
recent years has led to increased carelessness in the manner in which 
root grafts have been put together and to the use too often of inferior 
roots and scions. 
EXPERIMENTS ON THE BEST METHODS OF WRAPPING ROOT GRAFTS. 
Mention has been made of the tendency of root grafts to form 
excessive callus at the lower tip of the scion when stored under moist 
conditions in sawdust, excelsior, moss, and other similar materials. 
Where the two pieces of the graft are snugly fitted, there is little 
186 
