CANKKR OF THE APPLE TPvEE. 579 



EXPLANATION OF PLATE 32, 



Illustrating Dr. James E. BlomfiekVs paper on " Structure 

 and Origin of Canker of the Apple Tree," 



Fig. 1 is a photograph of branchlet of an apple representing the growth of 

 tliree years. Each gear's growth, numbered successively 1, 2, and 3, is 

 infected by Schizoncura, and sliows the characteristic boil-like swelling. 



Fig. 2 is a photograph of two sections, one through a normal stem, and 

 the other through a canker. At * tliere is a recent swelling caused by 

 Scliizoneura, 



Fig. 3 is a drawing of a slightly magnified section through a young tumour. 

 A is periderm commencing in tlie epidermis. B is the cortex. C is a 

 sclerenchyma strand. D is the bast. E is the cambium. F is the wood, 

 G is the tumour with a few large vessels cut across. 



Fig. 4 is a portion of a longitudinal section of tumour, x 700, showing the 

 pointed cells (W) which would have been wood-cells, and the square-shaped 

 cells (M) which represent modified medullary ray cells. 



Fig. 5 represents a portion of the tumour in the region of the cambium. 

 A are cortical cells. B are modified bast cells. C, modified cambial cells, 

 D, modified wood cells, E, the track of a seta with proliferating cells in its 

 neighbourhood, X 700. 



Fig. 6 shows a tumour passing into a condition of wound wood. The 

 enlarged wood cells are twisted, dislocated, and separated by collections of 

 cells, which represent the hypertrophied medullary rays. 



Fig. 7 represents iu a diagrammatic manner the changes undergone by a 

 cambium cell (A) iu becoming wood, and by an affected cambial cell. 



The series a to / represents the normal course; «' to/' the course under 

 the influence of the Schizoneura, with its cessation after a time 



