695 



Thus the difference of opinion extends to the most recent times^ with- 

 out having led to any positive reconciUation. The reason probably lies in 

 the fact that the characteristics given for the Sereh disease also occur in 

 other diseases, as will be shown, for example, in the following section, and 

 thus different investigators may have considered different forms of the 

 disease. 



We will emphasize a few facts from positive results, i. e. that healthy 

 cane can remain healthy in plantations suffering from the Sereh disease, and 

 that diseased cane remains diseased in healthy fields. It should be added 

 further that often wide bands along the edges of the fields appear diseased 

 first, or only the edges themselves, and that the Cheribon cane, which tends 

 to disease when planted in mountainous regions, has given healthy cuttings. 

 Some cuttings are practically immune, while others are susceptible. Even 

 the cuttings of the same variety from regions free from the Sereh disease 

 at first remain healthy, even in infected regions. It is evident from this that 

 the disease can scarcely be parasitic but falls under the group of the gum- 

 moses. It can, therefore, not be contested that the bacterial gummosis 

 conditions exist in the Sereh disease, just as in the rot of our sugar beets, but 

 these forms also depend upon certain conditions of weakness of the plant 

 body which we call displacement of the enzymatic functions. 



We consider the causes of the insufficient ripening of the cane, i. e. 

 non-deposit of reserve substances, cane sugar in this case, to be the inconsid- 

 erate cultivation of sugar cane with an increased supply of fertilizer and 

 water on heavy soil in enclosed positions, etc. Actually, the loss in the 

 sugar content is uncommonly great in the Sereh disease. 



We are not in a position to determine the process which causes the lack 

 of reserve substance. It is, however, a matter of indifference in judging of 

 the disease, whether an excess of destructive enzymes is present or a para- 

 lyzation of the constructive ones. The metaboUc processes, leading to this 

 lack of cane sugar, are naturally present in the whole plant no matter where 

 they make themselves felt symptomatically. Therefore, each smallest part 

 of the diseased cane, even if it shows no symptoms of the Sereh disease, is 

 actually predisposed to it and even contains the carriers of the disease. 

 Consequently each Bibit (cutting) from the plant having the Sereh disease 

 is condemned to death as soon as it comes under conditions favoring the 

 disease. It heals itself, however, and returns to the normal enzymatic 

 activity on tracts of land where the Sereh does not break out. 



From this the best method is clearly the choice of varieties immune to 

 Sereh or, at least, the cultivation of Bibits in open, mountainous positions 

 and other locaUties which do not permit the disease to occur. Probably a 

 change in cultivation takes place in such a way that only weak fertilizing 

 and more porous soils, as well as open positions, are used in the cultivation 



1 Hein, A. S. A., Hypothesen en Ervaring- omtrent de Sereh ziekte. De 

 Tndische Mercuur. Amsterdam 1905; cit. Jahresber. f. Pflanzenkrankh. v. Hollrung, 

 Vol. VIII. 1906, p. 245. 



