142 



BACTERIAL DISEASES OF PLANTS 





C^T"^: •"" ^ 



Fig. 73. — Cross-seetion of a cucumber stem (natural infection) showing the 

 spiral vessels occupied in each bundle by an enormous mass of deeply stained 

 Bacillus tracheiphihis. 1S94. 



Fig. 74. — Cross-s(H'tion of a ciicuniber stem showing location of Bacillus 

 tracheiphilus: 



A. Enlarged view of an inner bundle from Fig. 73, showing the bacterial mass 

 confined to the spiral vessels with the exception of two neighboring pitted vessels. 

 Around the spirals the bacteria have disintegrated the primary vessel parenchyma, 

 forming a small cavity. 



B. An outer bundle of Fig. 73. The occluded spiral vessels are surrounded 

 by bacterial cavities; most of the pitted vessels are empty. Photomicrographed 

 by the writer in 1894. 



