17 



Description of Plate II. 



Versfeld apple affected with bitter-pit cut across transversely, and 

 showing the distribution of the spots within the tissue of the apple. A 

 number of these spots are seen to occur well within the interior of the apple, 

 and are also closely connected with discoloui'ed vascular strands. 



Description of Plate III. 



Section through a bitter-pit spot in a Versfeld apple. A vascular 

 bundle is cut across transversely, and in close connection with it at the 

 upper part of the section is shown the general appearance of the enlarged 

 and collapsed cells with their enclosed starch-grains such as are usually 

 met with in the bitter-pit spots. In the lower part of the section the 

 normal cells are shown, and it will be seen that they have thinner walls, 

 are devoid of starch-grains, and ai-e of smaller size than those which 

 compose the bitter-pit spots. 



• Description of Plate IV. 



Fig. 1. — Micro-photograph of a section through a part of " Lord 

 Wolsey " variety. A vascular bundle is cut across transversely, and 

 surrounding it a jiumber of the cells are seen to be enlarged, and a certain 

 amount of bursting and collapse has taken place. 



Fig. 2. — Micro-photograph of a section through a bitter-pit spot at 

 an early stage of its development. A vascular bundle is cut across trans- 

 versely, and leading away from the bundle to the right is a mass of broken- 

 down cells, which have numerous starch grains imprisoned between the 

 collapsed walls. Owing to the low magnification used, the individual 

 starch grains cannot be clearly made out in the micro-photograph. (Lord 

 Wolsey variety.) 



Fig. 3. — Micro-photograph of a section through a bitter-pit spot in 

 the Versfeld variety. The collapsed and broken-down cells are seen to be 

 closely connected with a vascular bundle, which is cut across transversely. 



Fig. 4. — Micro-photograph of a section through a bitter-pit spot in 

 the Versfeld variety. Between the epidermis and the vascular bundle 

 the necrotic area is clearly seen. The cells in this region have thicker walls 

 than those in the surrounding healthy parts. Some of them are very 

 much enlarged, while many have collapsed, leaving large irregular inter- 

 cellular spaces. The vascular bundle seen in transverse section is closely 

 associated with the diseased spot. 



Description of Plate V. 



Fig. 1. — Micro-photograph of a section through a bitter-pit spot in 

 the Versfeld variety. The vascular bundle is cut through just at the point 

 of branching, and is seen partly in transverse section and partly in longi- 

 tudinal section. The diseased cells can be traced directly to the bundle. 



