DESCRIPTIONS OF PATHOGENIC BACTERIA. 209 



fungi, occur in a remarkable plant disease, 

 the " finger and toe disease " of cabbages ; Wor- 

 onin called this myxamceba, Plasmodiophora 

 brassicce. 



In some diseases of plants, bacteria may ap- 

 pear as the exciting cause, but as a rule the 

 acid reaction of plant tissue hinders bacterial 

 growth. The wet-rot of potato is caused, ac- 

 cording to Reinke and Berthold, by an endo- 

 sporous bacillus which penetrates the interior 

 when the cork layer is injured. According to 

 Wakker, the " yellow" disease of hyacinths in 

 Holland is due to bacteria which occur in 

 yellow slimy masses in the vessels of the bulb 

 and in the vessels and parenchyma of the 

 leaves. Ad. Mayer considered the mosaic 

 disease of tobacco leaves to be due to bacteria, 

 and Arthur attributed a widely-spread disease 

 of the pear-tree in America to a species named 

 M. amylovorus. 1 



Among men and domestic animals there are 

 some diseases caused by microbes belonging 

 to the group of animals, known as Protozoa ; 

 the taxonomic position of these organisms is 

 still in controversy, however. The disease 

 known as surra, a severe and often fatal 



1 An excellent summary of the present state of our knowledge 

 regarding bacterial diseases of plants is given by Erwin F. Smith, 

 in the American Natitralist, Aug. 1896, pp. 626 et. seq. E. O. J. 

 14 



