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as found by Dr. Sturgis, the writer has never seen such a case and 

 can state positively that no such organism is the cause of the disease 

 now under consideration. The roots of all the affected plants exam- 

 ined have been perfectly clean and healthy. 



The presence of lice in the roots has been thought 

 Root Lice, by some to bring about the disease, but only a very 



brief examination is needed to show the incorrect- 

 ness of this idea. Where this pest is abundant numbers of plants 

 may be found whose roots are covered with lice but which still show 

 no sign of the yellow disease. It is indeed quite evident, on close 

 examination, that these pests are much more abundant upon normal 

 than upon diseased plants in the same bed. 



It is natural in a plant disease to look for some par- 

 Fungi, Bac- asitic organism as the cause. In many respects the 

 teria, or other appearance and nature of this disease lead one to 

 Organisms, suspect some such origin, but it may be said at once 



that the most careful search in all parts of the plant 

 has failed to reveal anything of the sort. That the trouble is purely 

 of a physiological nature, due to some perversion of the normal func- 

 tions of the plant can scarcely be doubted. 



The trouble is equally prevalent upon all varieties 

 Varieties. of asters. Besides the large amount of evidence 



on this point obtained incidentally in the course of 

 this work from our own plants and those of many other growers, this 

 matter was especially tested in the summer of 1900. Seed was 

 obtained of all the varieties of any importance obtainable in the 

 country, over three hundred separate lots in all, and the plants of 

 each kind set out in one long bed for comparison. The result was 

 that while naturally some variation in the amount of disease 

 occurred, no important difference could be seen in favor of or against 

 any variety. It is interesting to note that the alleged " original " 

 aster obtained of Heinemann, of Erfurt, (ierman}^ was one of the 

 worst affected varieties. 



In purchasing seed care was taken to inquire in 



Source of each case where it was grown. In this way a com- 



Seed. pari son was instituted between plants from seed 



grown in Germany, France, England, California, 

 New York, and Massachusetts. No difference whatever appeared. 



