220 



U. SUZUKI. 



(IV) . By layering i,e. burying a portion of the diseased 

 shoots bent into the earth, as shown in PI. XXXVII-XXXIII. 

 The new rootlets are produced from the covered part, and absorb 

 nutriments from the soil, and the shoots recover from the disease. 

 Numerous experiments have shown this fact, and even the 

 severet cases of the disease may sometimes be successfully 

 treated in this way. See Plates XXXVIII-XXXVIII. 



(V) . By keeping diseased plants from cutting for two or 

 three years and well manuring, many can be made to recover, 

 as has been proved by many experiments. But if these plants 

 are again cut in the growing season they will become again 

 diseased. Further, if we cut down the diseased shoots in early 

 spring before the leaves are developed, the next new shoots 

 will grow normally. This may be explained by considering 

 that the roots of diseased plants may still contain a moderately 

 large quantity of reserve materials during the winter, if they 

 were kept from cutting ; so that the new shoots may develop 

 normally without suffering from the deficiency of reserve 

 materials. In the experiment made in 1898, in which 22 diseased 

 plants were kept from cutting, 1 1 plants recovered and 3 more 

 showed signs of imperfect recovery. In another experiment 

 made in the same year 15 recovered out of 22, while those that 

 were subjected to cutting in the growing season, did not only not 

 recover, but became even more severely diseased. The result 

 obtained in 1899 is equally interesting, 13 plants having recovered 

 out of 22 diseased plants ; while in the case of plants subjected to 

 cutting none recovered. 



(VI) . After cutting in the growing season, a considerable 

 amount of the sap flows out from the cut stems for several days, 

 amounting sometimes to several hundred cubic centimenters for 

 one plant. And as this sap has been believed by many to have 

 an intimate relation to the exhaustion of the reserve materials, 

 I have directed my attention to its chemical analysis. For 

 collecting the flowing sap India rubber tubes were connected 

 at one end with . the cut stems and at the other with tightly 

 corked test tubes. 



a). Sap of Obata. Collected on May 20. 



Colour. — Slightly turbid ; after standing for several 

 hours, a little precipitate was formed at the 

 bottom, 



