24 



CAUSE AND NATURE OF CROWN-GALL 



Fig 5.— Diseased almond seedling resulting from inoculating a healthy seedling by 

 making an incision through the bark and inserting a bit of fresh gall tissue. A small 

 lateral root shows a large gall completely surrounding it, which developed later. 



point fully three inches above the ground on the stem of the 

 tree. Four similar seedlings were also inoculated at the crown 

 with bits of a blackened, decayed gall placed beneath incisions 



made at the crown. 



The twenty seedlings above 

 noted were left undisturbed until 

 November 10, 1899, when the}' 

 were again pulled up and exam- 

 ined. Without a single excep- 

 tion all were badly diseased. The 

 old gall seemed to be as effective 

 in producing the disease as the 

 young tissue. In every case galls 

 had developed at the places where 

 the incisions were made. In many 

 instances, however, galls devel- 

 oped deeper down on the roots 

 as well. It is probable that the 

 galls which appeared at places 

 where no incisions were made 

 were caused by the spreading of 



Fig. 6. — Diseased almond seed- 

 ling showing two galls, both the 

 result of making incisions through 

 the bark and inserting bits of gall 

 tissue. The larger gall developed 

 at the crown, under ground ; the 

 smaller one on the stem, two or 

 three inches above the surface of 

 the soil. 



