THE SEREH-DISEASE OF SUGAR-CANE. 77 



disease. This very thing was done on the place of Kemanglen. Naturally the plantations did not 

 take much room, but every year new bibit was taken from the externally healthiest stems. In 1887 

 the Sereh-disease first took a violent form at Kemanglen after having shown itself in a light degree for 

 some years, and since that time the original reed was propagated in the above manner with this result: 

 that every year less Sereh-symptoms showed themselves and that the plantation at this time April, 

 1 893 does not show one per cent of Sereh (Went) . 



Wakker states that the following varieties are entirely free from Sereh : Fidji koening, 

 Kerah-cane, and a few others, while Loethers, Muntok, and Manila cane are sufficiently free 

 to supplant the Cheribon to advantage until such time as entirely resistant canes can be 

 obtained from seed-plants. All canes derived from seed are not resistant, but some appear 

 to be (Went) . The disease may be finally rooted out of the plantations by the selection each 

 year of sound cuttings for propagation. This has been done not only at Kemanglen, but also 

 in a small way (1891 to 1896) at the West Java experiment station (Went). 



None of the Dutch writers have brought any conclusive evidence as to the parasitic 

 nature of Sereh, i. e., they have not established the constant presence of any particular organ- 

 ism in the diseased cane ; neither have they shown that the disease can be induced in sound 

 cane by inoculating any particular organism. At the same time no thorough bacteriological 

 study appears to have been made. 



Wakker's views as to the origin of this disease are that it is due to the degeneration of 

 cane under the influence of alternating seasons of great rainfall and of drought, such being 

 the climate of the Javan plains. More explicitly stated, the west monsoon prevails for 5 

 months in the year, December to April, and each month there is a very heavy rainfall, the 

 total precipitation during this period often amounting to several meters. During the re- 

 mainder of the year the east monsoon prevails and a drought occurs, the total precipitation 

 amounting to only a few centimeters. The cane is set out in the dry weather and watered 

 for several months, i. e., until the west monsoon prevails. It then grows with enormous 

 rapidity for 5 months, whereupon follows a second period of drought in which the root- 

 system gradually fails, the cane obtains barely water enough to keep alive, and so comes to 

 maturity and the harvest time, about 12 to 15 months from planting. I translate from 

 Wakker's final paper as follows : 



In brief, the Sereh-disease is a gum-disease of the stem, which is caused, not by parasites, but by 

 insufficient water-supply, the influence of which is greater on the future generation than on the plant 

 itself. I have expressed this by saying that the disease is hereditary and accumulative. 



He discusses this view very ably in a paper of 70 pages. I quote from this further as 

 follows : 



I shall add directly that my presentation departs altogether from every other which has thus far 

 been published and especially in that I consider the Sereh-disease as non-parasitical and so also as 

 non-infectious. * * 



I too, at first thought of trying to find the parasite of the Sereh-disease. A number of attempts 

 to get it by preparations of the stem have cost me much time, and led me to this one positive result 

 the conviction that it is not to be found there. * * * 



The variety of the Heterodera found by Treub I have never met with in sugar-cane roots, and it 

 belongs at most to the rare parasites of that plant. A parasitic Tylenchus variety no man has ever 

 seen yet. * * * 



An examination made by me of these red stripes [in the stem] gave proof that in them or in their 

 vicinity no parasites occur. * * * 



No one has found Sereh-diseased plants in a wild state. * 



So far as I know, Janse is the only one who mentions the case in which Sereh-diseased bibit set 

 out in the open ground at Buitenzorg produced healthy plants. 



One other matter is to be mentioned here. If, from year to year, slips of Sereh-diseased plants 

 are set out, this does not lead to a dying out of the cane. In other words, Sereh-diseased plants, even 

 when severely attacked, may always still provide slips for the growth of new plants, at least when 

 they are not too old. * * * 



A cane plant may very well have a vigorous root-system and yet be typically Sereh-diseased. 



