Chyptogamic Botany and Plant Pathology. 



405 



that this disease-d area, quite small primarily, and iseated only 

 upaa <5iiie side of the twig, gradually increased in size until eventu- 

 ally it extended entirely ai'ound the twig completely girdling it. 

 The supply of nutriment thus being cut off from the tenninal 

 portion of the twig, death of that pontion followed. 



Seatied in the original diseased areas, whether extending partly 

 or entii'ely around the stem, are minute black elevated points 

 which can be seen with the unailded eye. Figure 1 a and b repre- 

 sent portions of twigs, a with the diseased ai^a extending partly 

 around the stem, while b is girdled. In the diseased areas are 

 shown these small black elevations. The diseaise is produced by 





a fungus which grows within the istem. These black elevated 

 points are centers where pustules of the fungiis are developed con- 

 taining its reproductive bodies, or spores. 



Fig. 2 represents a very thin section, across one of these pustules, 

 magnified to show the stnicture of the pustule and the form of the 

 pores. The growth of the pustule has ruptured the epidermis of 

 the stem. In the opening between the broken parts of the epider- 

 mis are shown some of the spores. Beneath these are numerous 

 parallel short fruiting threads^ or basidia of the fim^gus, at the end 

 of wliich the spores are developed. The basidia can be seen to 

 anse from the blackened stiM>ma of the fungus which consists of 



