MULBERRY-DWARF TROUBLES IN JAPAN. 



287 



disease had appeared shortly before the examination was com- 

 menced. 



The healthy roots contained much more starch than the 

 diseased ones and further there was a remarkable difference in 

 the thickness of the rooot bark, that of the diseased one being 

 only \ — as thick as that of the healthy one. 



4) . Takasuke. 



Some of the plants were subjected to cutting twice in 

 summer and the new shoots coming were repeatedly deprived 

 of the new leaves. Upon the appearance of the signs of a 

 severe disease they were examined on Oct. 12. Those which 

 remained still healthy under the same treatment, contained 

 some starch, while the diseased ones were almost entirely 

 deficient of it, a proof that the plants which used up the reserve 

 materials first became also first diseased. 



5) . Akagi, Oct. 12. 



Total carbohydrates. Total nitrogen. 

 Root bark of. Healthy. Diseased. Healthy. Diseased. 



Akagi (1) (cut in autumn) 17.0 10.3 — — 



Akagi (2) 14.5 13.7 — — 



Takasuke (twice cut) 16.2 15. 1 1.48 0.92 



The above experiments suffice to show that the disease 

 is evidently due to the exhaustion of the reserve materials in the 

 roots. 



Summary and Conclusions. 



My former view on the primary cause of the disease was 

 further confirmed by the experiments carried on in the last 

 year. It was experimentally proved that the bad development 

 and finally the decaying of roots in the diseased plants is 

 simply caused by the cutting in the growing season and is not 

 due to parasite attacks. The small rootlets which had grown 

 considerably, b fore cutting, lose their activity soon after 

 cutting and go gradually to decay. They do not develop anew 

 until 40-50 days after cutting when the new shoots had reached 

 50-60 cm. in height. The new shoots depend upon the reserve 

 materials in the roots until that time. It was further shown that 

 the root bark of those plants which had just commenced to show 

 the signs of the disease contained always less reserve material 

 than that of the healthy ones. The deficiency of reserve 



