6 THE CROWN-GALL AND HAIRY-ROOT OF THE APPLE TREE. 
Development of the forms of the disease—Continued. 
A study of nursery methods in root grafting, etc —Continued. 
The slight effect of using for root grafts scions from younger and older 
No effect from leaving a bud near the lower end of the scion in making 
root grafts... 2.22.2 setae eee eee eee ee 
Experiments comparing American and foreign-grown apple seedlings. 
The use of seedlings from old nursery districts for making root Ba 
may not increase the development of the disease........... : 
Heavy, wet soils favor the development of crown-gall in the nursery - 
Period for the maximum development of crown-gall and hairy-root in 
the nursery 2.222. 22 eee i ee ee 
Effect of the disease upon apple trees=- = 4 22— 2-5 oe ee 
Observations by others onjerown-call= 2]. 2222 ee 
Observations by othersion hairy-root.- 222-2 ----5--- 
Experiments on the effect of the disease on apple trees.........--.....---. 
Effect ontseedlings not uniionm = 3 - Sa. 2 ote eae eee 
Slight. effect on grafted trees in the nursery ..-.-.._..---.-2-2__4.__- 
Little or no effect on orchard trees shown in experiments....-.....-.. 
Experments:bysothers sees eae gee Jaa Nests ae aS 
Experimental orchards 522. ee ee 
Susceptibility of varieties of apple trees to the disease...........--....--.--.- 
Data upon a number of common varieties used in experiments.........--. 
Susceptibility of scions grown in different localities.....................- 
Communicability of the disease in the nursery and the orchard.............-- 
Previous publications on the communicability of apple crown-gall....._.. 
Previous publications on the communicability of hairy-roct.............- 
Experiments on the communicability of the disease. ...........--.-...-- 
Studies on the for.aation of callus as related to crown-gall..-.........- 
Studies on root formation as related to hairy-root....-.--....--..----- 
No communication of the disease to healthy uninjured seedlings...... 
The disease is communicable to wounded seedlings.....-..-.......-- 
Increase of the disease in root-grafted trees due to the inoculation of 
grafts... 2... ee 2. i a ee ee 
Increase of the disease due to poorly fitted root grafts............--.-. 
The use of scions from diseased trees increases the amount of disease. . 
The spread of the disease from tree to tree in nursery rows is almost 
negligible after the first years-2 = 95.2 ie ee 
Pruning and the grafting knives are not responsible for much of the 
disease... . 2. 2225.9 .22 Re ee ee eee 
Crown-gall not readily eoueninnnceies to dormant trees stored in 
bundles... =: 2.22224: 51225 So Sa 
The disease only slightly communicable in orchards............--..- 
Prevention and cure... 2:5... 23. gee ee 
Probable futility of attempts at preventiom==25-= === = eee 
Methods for the control of the disease in nursery bins........--......----- 
Propagation of susceptible varieties of apple trees by budding.-....... baee 
Improvement in methods of reoteraftings.- 9) a ee 
186 
Selection of healthy scions mecessaryea--) eee 
Selection of healthy seedling roots mecessary--........-2...--..-.-_-- 
Careful fitting of root grafts neeessanyce === ae ee ee 
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