U. S. EXPERIMENT STATION BULLETINS. 



403 



we are accustomed to require for biological work, and the more the prob- 

 lem was studied the more this fact stood out. Very few analyses of the 

 peach had been made, and these did not fully agree. Additional analyses 

 were made at my request, and the conclusions from three of these are here 

 presented for the first time. Not to be tedious I shall give a comparative 

 statement, asking your attention only to certain striking discrepancies 

 Those who are specially interested will find the omitted details elsewhere. 

 According to the following authorities, peach branches when diseased 

 by yellows vary from healthy ones, as follows, omitting minor differences: 



Table I. — Showing the principal differences between healthy peach branches and 

 those affected by yellows, as determined by five chemists (14 analyses). 



From this comparison it will be seen that the analyses made under 

 direction of the department of agriculture (the last four) agree substan- 

 tially among themselves, but contradict the earlier analyses. In case of 

 the analyses by Professor Kedzie and Dr. Goessman, no statement is 

 made as to the exact age, location of parts, and relative proportion of the 

 various parts of the branches taken for analysis, and this renders them 

 practically valuless, because the amount of the various chemical constitu- 

 ents in a tree varies greatly according to the kind of tissue, the age, and 

 the location of the part. 



The analyses made by Mr. Knorr show that the diseased twigs contain 

 less lime and more potash and phosphoric acid than healthy twigs, and the 

 series made by Dr. Eastwood tend to confirm this view, although in one 

 instance he found slightly less P 2 5 and in another about the same K 2 O. 



The diseased branches collected for Mr. Knorr were the shoots of one 

 season. They had made a comparatively meager growth and were in a less 

 mature state than the corresponding healthy shoots. 



The shoots sent to Dr. Eastwood were of one season's growth, and 

 those in particular from Mr. Green's orchard were just as near comparable 

 as it is possible to get diseased and healthy growths. The diseased shoots 

 in each case had made a less robust growth and were slightly less mature 

 than the healthy ones, owing to the well known tendency of diseased 

 branches to continue feeble growths late into the autumn and to develop 

 unusually early in the spring. 



These results, reached independently by two competent chemists, upset 

 the old views completely, and are exactly what I was led to expect from 

 the well established physiological law that in the ash of the shoots of land 

 plants, lime increases and potash and phosphoric acid diminish in propor- 

 tion as the parts become well developed and approach maturity. To 



