696 



of cane; these also cause a standstill in the Sereli disease in distinct centres 

 of the disease. 



We believe also that the diseases termed the rusts of sugar cane belong 

 here. ( )f these, wc refer here to the Powdery Disease described by Spegaz- 

 zini'. which occurs also with red spots and a gummy secretion but becomes 

 noticeable because of its unpleasant smell. The base of the stem suffers 

 especially. A bacillus (Hacilliis sacchari) may be isolated from the gummy 

 slime which rcf|uires an acid nutrient sulistratiun and produces a protein 

 decay which gi\es rise to the otTensi\e smell of the diseased cane. This 

 disease also occurs with . liidropoiioii )iiilans In regard to the production 

 of the red color in the vascular bundles and of the gum in the sugar cane 

 by micro-organisms, Grieg vSmith's- work is of especial importance. He 

 found reddened vascular bundles in otherwise healthy cane as well as in the 

 stems which had become gummy because of Bacillus vascularum Cobb. The 

 red color was produced by the tilling of the large ducts with a red gum just 

 as in the Sereh and other sugar cane diseases. He found further a fungus. 

 wliicli produced a shiny, very scarlet color on nutritive media with dextrose 

 but no gum, and gum bacteria in the diseased ducts, especially Bacillus 

 Pseudarabinus n. sp. Bact. Sacchari ("this variety normally lives in the 

 sugar cane") and besides this Bacillus vascidarum. On sheets of nutrient 

 agar with laevulose, the fungus produces no coloring matter, but in combi- 

 nation with Bacillus pseudarabinus a bright scarlet is produced and in com- 

 ftination with Bact. Sacchari, a rusty brown. 



It will be seen from these examples how the constitution of the sub- 

 stratum is able to modify the ]^arasitic activity and in what way. therefore, 

 different aspects of disease are produced. A preliminary condition neces- 

 sary for the production of the disease is. however, a deviation from the 

 normal metabolic processes in cane, healthy up to that lime, which favors 

 an increase of bacteria (probably always ijresent) and which appears sooner 

 or Liter in the dilferent susceptible \arieties of cane but remains suppressed 

 in the innnune \arieties. 



Cop.b's Disf.asf. of the Sugar Cane. 



According to T'Twin .Smith", the .'^ereh disease resembles in many ways 

 the disease of the sugar cane occurring in Australia (and es])ecially in 

 jVIauritis, jaxa and lirazil), which Cobb describes. Hiis latter disease is 

 characterized b)' diminutive growth, shortening of the internodes, albinism, 

 premature sprouting of the buds, and i)ropagation by infected cuttings. It 

 diiTers essentially. howe\er, from the .Sereh, since the heart of the cane stalk 

 becomes lignilied and masses of yellow slime (gum) occur constantly in the 



1 Spegiizzini, T^a g.ingrona humida o polvillo do la carina de zucchfjo. Rivista 

 azucarera 1895. 



-' Smith R. Grieg, Sidney. Bakteriolog-. T^ahoratorium der Linnean Soc. of New 

 Soutli Wales. Central))!, f. liakt. usw. 1906. Vol. XV, No 25. p. 733. 



3 Smith, Krwin, Ursache der Cobb'schen Krankheit des Zuckerrohres. Central- 

 blatt f. Bakteriologie usw. 1904. Vol. XIII. Part 22, 23. 



