1897.] PUBLIC DOCUMENT — No. 38. 77 



The "rust" is quite common on the chrysanthemum leaves. 

 In the advanced stages it completely kills the leaf. It seems to 

 me that it is a very bad enemy to fight. I had plants enough to 

 bring seventy-five or a hundred dollars worth of flowers, and 

 I would not sell one flower, as I did not wish to have the name of 

 selling such flowers. The plants were grown in the garden and 

 "lifted" about the middle of September. The rust was on the 

 leaves at that time, and some of them were dead. 



The rust was in the uredo or red-rust stage, and i)roved to 

 be a form closely resembling and probably identical with 

 Puccmia Tanaceti, S. (P. Helianthi, D. C), which occurs 

 commonly upon Tanacetum vulgare (tansy), several species 

 of Artemisia (ragweed) and Helianthus (sunflower), and 

 several other related plants. Upon these plants it sometimes 

 acts most destructively, as it has done in this instance upon 

 the chrysanthemum. It bids fair to become a serious obstacle 

 to the cultivation of this valuable flower. 



Experience has shown that in the development by culti- 

 vation of any plant, as it becomes changed more and more 

 from its natural form and forced into an abnormal develop- 

 ment, its power to resist the attacks of disease becomes 

 diminished. For this reason reports of new diseases upon 

 our various cultivated plants are of frequent occurrence. 

 All such diseases are certainly not new in the sense of being 

 caused by a kind of organism which never existed before, 

 but only new upon some particular kind of plant, Avhich has, 

 by reason of its forced and abnormal development, lost the 

 power to resist the attacks of the parasite, which has ex- 

 isted all along upon some other kind of plant, and very 

 likely in a milder form. 



The chrysanthemum in its present form is a comparatively 

 new plant in this country. Its great popularity has led 

 growlers to make extraordinary eflbrts to force its develop- 

 ment along certain lines, notably in size of flowers. The 

 production of flowers eight inches in diameter by a plant 

 destined by nature to produce them less than quarter that 

 size cannot be accomplished without bringing about serious 

 changes in the vital functions of the plant, and making it 

 more susceptible to disease. Therefore the list of chrysan- 

 themum diseases may be expected to gradually increase, as 



