PLATE 7 
A. —Primary root infection of Mercereau blackberry No. 352 C. The parent plant 
giving rise to the horizontal root now showed a large healthy cane in blossom. A 
root 18 inches long and one-half inch in diameter branched freely at 12 inches, 
then gave rise to a slender runner; at b, 14 inches from a, a stub end of a 1921 cane 
cut off accidentally; 32 inches farther, two new shoots, infected, from a swollen region 
of the runner. Sections of the root at c, c 2 , and c 3 showed no mycelium. Sections 
at c 4 of the new shoot showed hyphae in the pith only. This is clearly a case of root 
infection, although no wound scar is visible. 
B. -—Root attached to No. 357 E, a Kittatinny blackberry showing a case of primary 
root infection. The parent plant, at the right, was normal, free from rust, and bearing 
blossoms. Wound callus or scar on the root at w shows where the parasite entered 
the cortex of the root which lay very near the surface of the ground. No mycelium 
was found in the horizontal root at x, y, and z. See text for further discussion. 
