New Yorx AGRICULTURAL EXPERIMENT STatTion. 289 
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INTRODUCTION. 
The name.— As stated by von Schrenk, in a short note on a 
fungus root-rot of apple trees, the term root-rot is too broad 
and probably includes several distinct diseases, some of which 
may be caused by parasitic organisms, others by adverse en- 
‘vironment and some probably by both. Only a detailed study 
of the factors concerned in causing this group of troubles will 
permit a diagnostic arrangement of the separate diseases. The 
term Crown-rot or Collar-rot is possibly rather indefinite too, 
for it also includes a rotting of the upper roots and sometimes 
partial decortication of the trunks. Though this may be only 
a group name, it is used here (till some more accurate term 
can be found in the action of the primary cause) to designate 
fruit-tree injuries which usually begin at the collar, near the 
ground line and frequently at the uppermost roots, and extend 
irregularly both up and down, browning and killing bark and 
wood. (See plates XITI-XV1.) 
The causes.— From a brief review of available literature of 
root-rots, crown-rots and other winter-injuries, as well as my 
recent observations, it seems that this disease is perhaps pri- 
marily due to adverse meteorologic and soil conditions, though 
another factor has been advanced as the primary cause of a 
disease of this type. It seems improbable that it may be 
caused by parasitic organisms, yet they are possibly factors in 
the later stages of the malady; after the normal functions of 
the trees have been sufficiently disturbed and some of their 
tissues killed. Opinions expressed in print seem mostly to 
agree as to the principal causes, but differ somewhat regarding 
the details of their operation. The relations of the significant 
factors are variously stated and possibly some of the important 
ones are still overlooked. 
The problem.— Injuries of underground parts are not as 
easily studied as diseases of aerial structures, and then too, 
several only partially known factors may be involved in crown- 
rot. How is the stock, upon which the variety is grafted, 
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