CAUSE AND NATURE OF CROWN-GALL 



35 



Figs. 12 and 13 show sections through both stem and root 

 with galls attached. In these specimens the galls have com- 

 pleted their growth and the outer portions have begun to dis- 

 color to greater or less depths. These illustrations are excellent 

 examples of the mode of attachment of fair-sized galls to the 

 roots and stems. 



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Fig. 13. — A longitudinal sec- 

 tion through the crown of an 

 almond seedling and attached 

 gall, showing the darkened, dis- 

 colored outer portion of the gall 

 tissue a short time after growth 

 had ceased. 



Fig. 14.— A portion of the stem of a 

 seedling almond, twice natural size, 

 showing the returning hypertro- 

 phied tissue after excision of the gall. 



When the gall decays, as it usually does at the end of the 

 season's growth, it leaves an open wound through the bark, 

 which extends for some distance into the wood. The following 

 spring a more or less interrupted circle of gall tissue begins to 

 form around the margin of the wound caused by the gall of 

 the previous year. The wound becomes larger and deeper with 



