COMMUNICABILITY OF THE DISEASE. A7 
of 50° to 60° F’. and the other in a greenhouse at a temperature of 
65° to 90° F. 
Both series were packed in sterilized jars in a number of different 
kinds of packing. The jars and substances used in packing were 
sterilized in an autoclave at a temperature of 239° F. for three hours. 
The sets were placed under the following conditions of moisture in 
the cellar and the greenhouse: (1) Moist sphagnum moss; (2) moist 
sand; (3) moist sawdust; (4) moist soil; (5) moist chopped excelsior ; 
(6) moist air over water, surrounded by wet blotting paper; (7) all 
but the tips of the upper ends in water. 
In nursery practice root grafts are made and either planted out 
immediately or stored in moist conditions until the wounds are filled 
with callus. Of the two sets of root grafts in the experiment those 
placed under the cooler conditions formed callus about one-half as 
rapidly as those in the warmer conditions. Those in the warmer - 
conditions, had they been in the nursery, should either have been 
planted at the end of ten to fourteen days or placed in cold storage 
to inhibit further development of callus. Those in cooler conditions 
were ready to plant in three to four weeks, and at the end of six 
weeks the formation of callus had become excessive, especially in 
moist moss, earth, sawdust, and chopped excelsior. Sand was found 
to be much the best for packing root grafts, since only a moderate 
formation of callus took place. In this substance there was no exces- 
sive formation of callus except in a few cases when the period of time 
in the cellar was extended to two months. The grafts, however, after 
two months in the cellar or one month on the benches had begun to 
form shoots and roots, and for this reason were not in good condition 
for planting. 
The experiment gave the following general results: 
(1) On apple cuttings callus formed readily but not excessively in 
spiral and cross incisions, and less readily in longitudinal incisions, 
filling the cuts with new tissue, and in the former often projecting 
from the surfaces in small outgrowths. 
(2) Usually no callus developed from the upper cut of cuttings, 
seedlings, and scions, whether cut off slanting or square. If any was 
formed, it barely showed above the surface of the cambial layer. 
(8) Under moist air conditions, either in moss, sand, sawdust, soil, 
or in the open air, callus formed readily on the lower cut ends of cut- 
tings, seedlings, and scions. In time it formed excessively developing 
outgrowths half an inch or even more in diameter. 
(4) In root grafts in time callus formed excessively under the con- 
ditions mentioned in the preceding paragraph at the lower pointed 
end of all the scions and at the lower cut ends of some of the roots in 
the grafts (Pl. VIII, fig. 2). The graft union was closed with callus 
186 
