76 BACTERIA IN RELATION TO PLANT DISEASES. 



His manner of treating the surface would seem to indicate that these spore-bearing 

 organisms were present, sometimes at least, in the interior of the cane, but, of course, they 

 show nothing as to the cause of Sereh. The most interesting thing, perhaps, in his paper is 

 the effect of copper sulphate on the cane-plant. He found that Janse's bacteria were able 

 to endure a strong solution of copper sulphate, and also that the cane-plant itself was not 

 easily injured by this chemical. Cane-stems placed in a strong copper sulphate solution and 

 left for weeks germinated, and when planted out grew into good plants. He states that 

 Kobus could not discover a single plant affected by Sereh in English India. 



The probability is that the organisms obtained by Janse came either from the surface of 

 the cane or from dead leaf-traces in the nodes. His cane-disks were certainly insufficiently 

 sterilized by the boiling, and his Bacillus sacchari seems to have behaved in culture-media 

 very much like the common potato bacilli, i. e., it yielded a wrinkled growth, was extremely 

 aerobic, produced spores promptly, etc. Dr. Went says of it : 



I will presume that I hold the bacteria which Janse calls Bacillus sacchari to be identical with or 

 at most a tropical variety of a bacterium generally known in Europe the hay-bacillus (Bacillus sub- 

 tilts). It is remarkable how much these two resemble each other. 



Debray states that he repeated Janse's experiments and got similar results whenever 

 the surface of the cane was imperfectly sterilized, but nothing at all when it was properly 

 sterilized. 



Went states that out of the gum-diseased vascular bundles he obtained by cultures some- 

 times nothing at all and at other times various bacteria, but no one constant form. It 

 would appear, however, from the following paragraph that Dr. Went did not put much time 

 on the question of a bacterial parasite : 



From lower plants I directed my attention particularly to moulds and left the bacteria entirely 

 outside the scope of my investigations, especially because the number of plant diseases which are 

 actually caused by these little creatures now so much in fashion is so very small. Only when it 

 appears that moulds can not possibly be the cause of the leaf-sheath disease, I will occupy myself with 

 bacteria. 



From a study of healthy mountain cane planted on the plains and becoming subject to 

 the Sereh, Went reached the conclusion that the red vascular bundles took their origin where 

 the leaf-sheath joins the stem (see Cobb's disease, p. 53). Went also states that Kriiger 

 reached the same conclusion. In his type 4 (those plants least diseased) Went states that 

 there are no external signs of the disease and that the internal signs are confined to the nodes. 



Mountain plantations, if set with sound bibit, are at first free from Sereh, but they also 

 finally become infected (Valeton, Went). The custom in Java, therefore, for some years 

 was to bring down cuttings of sound mountain cane into the valleys for use in the sugar- 

 fields. The first year's crop was generally sound. If cuttings were taken from these the 

 following year for the fields, then generally some Sereh apppeared ; and in the third and fourth 

 years much more than if the plantations were renewed each year from mountain cuttings. 



The variety most commonly cultivated in Java at the time Sereh prevailed so exten- 

 sively was the Black Cheribon cane. In many instances, in recent years at least, this cane 

 has been discarded and more resistant varieties planted. Borneo cane is also very suscep- 

 tible. It is now known that there are a number of quite resistant canes. While not abso- 

 lutely immune to Sereh, the Louziers cane (called also Loethers) and the Muntok cane are 

 very little susceptible to Sereh (Went) . The Fidji or Canne Morte and the Manila cane are 

 absolutely Sereh-free (Went). The wild canes Glaga and Glongong and the Teboe Kassoer 

 are free (Went). 



So, by taking each year bibit from those canes which show the least marks of Sereh, one must 

 gradually get a variety which outwardly indeed does not differ from Cheribon reed ; but inwardly pos- 

 sesses the great difference of being immune or at least tolerably proof against the attack of the Sereh- 



