THE BIOLOGY OF BACTERIA 35 



ing a double poisonous property, an intracellular poison and 

 a toxin. In this latter class would be included the bacilli of 

 Anthrax and Tubercle. 



Reference has been made to the associated work of higher 

 vegetable life and bacteria. The converse is also true. 'Just 

 as we have bacterial diseases affecting man and animals, so 

 also plant life has its bacterial diseases. Wakker, Prillieux, 

 Erwin Smith, and others have investigated the pathogenic 

 conditions of plants due to bacteria, and though this branch 

 of the science is in its very early stages, many facts have 

 been learned. Hyacinth disease is due to a flagellated 

 bacillus. The wilt of cucumbers and pumpkins is a common 

 disease in some districts of the world, and may cause wide- 

 spread injury. It is caused by a white microbe which fills 

 the water-ducts. Wilting vines are full of the same sticky 

 germs. Desiccation and sunlight have a strongly prejudicial 

 effect upon these organisms. Bacterial brozvn-rot of potatoes 

 and tomatoes is another plant disease probably due to a 

 bacillus. The bacillus passes down the interior of the stem 

 into the tubers, and brown-rots them from within. There 

 is another form of brown-rot which affects cabbages. It 

 blackens the veins of the leaves, and a woody ring which 

 is formed in the stem causes the leaves to fall off. This 

 also is due to a micro-organism, which gains entrance through 

 the water-pores of the leaf, and subsequently passes into the 

 vessels of the plants. It multiplies by simple fission, and 

 possesses a flagellum. 



There can be no doubt that these complex biological pro- 

 perties of association and antagonism, as well as the parasitic 

 growth of bacteria upon higher vegetables, are as yet little 

 understood, and we may be glad that any light is being shed 

 upon them. In the biological study of soil bacteria in 

 particular may we expect in the future to find examples of 

 association, even as already there are signs that this is so 

 in certain pathogenic conditions. In the alimentary canal, on 



