23 



For further study in this direction equal weights of badly diseased 

 and normal leaves were gathered and ground in a mortar to pulp. 

 The addition of a considerable amount of fine quartz sand greatly 

 facilitates the grinding. Ecjual amounts of distilled water were then 

 added to each portion and the decoctions allowed to stand over night, 

 first adding a few drops of chloroform to prevent the growth of 

 molds or bacteria. The solutions thus obtained show several con- 

 stant differences. That from diseased tissue is decidedly acid, while 

 the normal is neutral or very nearly so. This difference becomes 

 very marked on standing a short time. The diseased has also a 

 sour, unpleasant odor, quite different from that of the other. When 

 tested by the Guaiac method the diseased always shows much less 

 oxidase and peroxidase reaction than the normal. With ferric chlor- 

 ide the diseased shows much more fanniii than the other. Equal 

 quantities of the two solutions were added to equal amounts of a sat- 

 urated solution of corn starch in water, showing with iodine a deep 

 blue-black color. After standing fifteen hours the normal leaf solu- 

 tion gave no more blue color, showing diastase had been present in 

 the tissue sufficient to convert the starch into sugar. In the diseased 

 solution a strong starch reaction still took place, re-affirming the 

 results obtained by treating entire leaves that diastatic action is very 

 weak in affected leaves. The same result was also obtained bv add- 

 ing to the starch solution a powder made by drying the leaves and 

 grinding them as finely as possible. 



In the same way solutions were made and tested, using diseased 

 and normal flower heads and buds, with no green parts included. 

 These decoctions showed much viore oxidase and peroxidase in the 

 diseased X.h'An in the normal ; the reverse of the results with leaves. 



To sum up, these results indicate that in plants affected by the 

 yellow disease the leaves have the power of assimilation or starch 

 formation, but are deficient in diastatic and oxidizing action and 

 contain an abnormal amount of tannin and acids. In parts not nor- 

 mally green and therefore having no assimilative function, oxidation 

 is more than normally active. The latter symptom is of ordinary 

 occurrence as a siamaiioii phenomenon, and may therefore be attrib- 

 uted to the lack of nutrition brought about by the failure of dias- 

 tatic, and perhaps other forms, of metabolic action in the leaves. In 

 the leaf itself the results are not sufliciently complete for drawing 

 broad or general conclusions. The presence of abnormally large 



